# DimMath

> Shipping calculation tools and logistics reference guides for US e-commerce sellers. Some tools run in the browser; DIM Weight and Carrier Savings also call DimMath's estimate API. Results are not live carrier quotes. Carrier and Cubic tools are US domestic. Amazon tools use US marketplace FBA. Import duty estimates US entry fees for goods imported into the United States; destination VAT/GST is labeled separately.

DimMath provides calculation engines and reference documentation for e-commerce parcel shipping, Amazon FBA fulfillment, USPS cubic pricing, and international import landed costs. Local math, DimMath-hosted estimates, and reproduced published rate cells are different things. Carrier APIs are not used.

## Calculators

- [DIM Weight Calculator](https://dimmath.com/dim-weight-calculator/): Compare dimensional weight against actual weight and check rates across UPS, FedEx, USPS Ground Advantage, and USPS Cubic with multi-box support.
- [UPS DIM Weight Calculator](https://dimmath.com/ups-dim-weight-calculator/): UPS Daily package DIM locked to divisor 139 and ceiling rounding from the 2026 UPS Rate & Service Guide.
- [FedEx DIM Weight Calculator](https://dimmath.com/fedex-dim-weight-calculator/): FedEx DIM modeled at divisor 139; 2026 FedEx Rate Guide PDF not independently verified.
- [USPS DIM Weight Calculator](https://dimmath.com/usps-dim-weight-calculator/): USPS Ground Advantage and Priority Mail DIM divisor 139 when billed volume exceeds 1,728 in³ (July 12, 2026).
- [Smart Box Finder](https://dimmath.com/box-size-finder/): Calculate optimal carton dimensions for single and multi-item orders to eliminate wasted volume and avoid dimensional weight price jumps.
- [Carrier Savings Engine](https://dimmath.com/carrier-savings-engine/): Compare commercial shipping rates across USPS, UPS, and FedEx for zones 1–9 to identify the lowest-cost carrier for any package weight.
- [Amazon FBA Fee Calculator](https://dimmath.com/fba-fee-calculator/): Calculate Amazon US FBA fulfillment fees, storage fees, low-inventory fees, size tier classifications, and net profit margins.
- [FBA Prep Cost Calculator](https://dimmath.com/fba-prep-calculator/): Compare the total cost of prepping Amazon FBA inventory in-house versus third-party prep centers (3PL) versus Amazon Prep Service.
- [USPS Cubic Calculator](https://dimmath.com/usps-cubic-calculator/): Determine USPS Ground Advantage Cubic (10 tiers, 0.1–1.0 cu ft) and Priority Mail Cubic (5 tiers, 0.1–0.5 cu ft) eligibility and commercial discount rates.
- [Total Landed Cost Calculator](https://dimmath.com/total-landed-cost-calculator/): Compute complete per-unit landed costs including manufacturing COGS, ocean/air freight, customs tariffs, port fees (MPF/HMF), and shipping insurance.
- [HTS Code Lookup](https://dimmath.com/hts-code-lookup/): US-only HTS planning search by product, material, use, or digits. Hands off clean ad valorem percents to the Import Duty Calculator. Not a ruling.
- [HS Code & Duty Estimator](https://dimmath.com/hs-duty-estimator/): Estimate US duties and MPF for goods imported into the United States (not US duties on exports). Destination VAT/GST labeled separately.
- [Commercial Invoice Generator](https://dimmath.com/commercial-invoice-generator/): Browser-only Commercial Invoice, CN22, and CN23 PDF templates. No sign-up. Field values are not sent to DimMath.
- [Oversize & Additional Handling Calculator](https://dimmath.com/shipping-surcharge-calculator/): Evaluate US domestic UPS, FedEx, and USPS additional-handling, large-package, and USPS nonstandard triggers from DimMath rate config.
- [Shipping Software Comparison](https://dimmath.com/shipping-software/): Review commercial shipping platforms (ShipStation, Pirate Ship, Shippo, EasyShip) and discounted carrier rate access for e-commerce stores.

## Guides

### Dimensional Weight

- [What Is CBM in Shipping and How Do You Calculate It Correctly](https://dimmath.com/blog/what-is-cbm-in-shipping-and-how-do-you-calculate-it-correctly/): CBM is how ocean freight carriers price your shipment. Get the formula, worked examples, container sizes, and the LCL vs FCL rule.
- [FedEx vs UPS Dimensional Weight – Which Carrier Bills More?](https://dimmath.com/blog/fedex-vs-ups-dimensional-weight-which-carrier-bills-more/): FedEx and UPS both use divisor 139 but apply DIM weight differently. Here is which one bills more for your package.
- [Dimensional Weight International – 139 vs 166 vs 5000](https://dimmath.com/blog/dimensional-weight-international-139-vs-166-vs-5000-divisor-map/): International DIM weight divisors : 139 for UPS/FedEx, 5000 metric for DHL, 6000 for air freight, Canada Post split. Same package compared at every divisor
- [Poly Mailers vs Boxes: Which Costs Less in DIM Weight](https://dimmath.com/blog/poly-mailers-vs-boxes-dim-weight-impact/): Poly mailers vs boxes: DIM weight comparison, dollar savings per shipment,ceiling rounding impact & the hybrid approach that cuts costs.
- [Void Fill Guide – Air Pillows vs Paper, Cost Per Shipment](https://dimmath.com/blog/void-fill-guide-air-pillows-vs-paper-cost-per-shipment/): Void fill cost per shipment: air pillows, kraft paper, packing peanuts compared. DIM weight cost of excess void fill, FBA prohibited materials & when to fix the box.
- [Dimensional Weight Shopify – How Shopify Calculates It](https://dimmath.com/blog/dimensional-weight-shopify-how-shopify-calculates-dim-weight/): How Shopify calculates dimensional weight in 2026: no native dimension fields, default box risks, ceiling rounding impact and how to fix checkout rates.
- [Box Size Optimizer for Multiple Items – Pack Calculation](https://dimmath.com/blog/box-size-optimizer-for-multiple-items-pack-calculation/): Multiple item box sizing in 2026: one box vs two boxes decision, combined DIM weight math, USPS Cubic eligibility, and ceiling rounding impact.
- [How to Choose the Right Box Size – DIM Weight Impact](https://dimmath.com/blog/how-to-choose-the-right-box-size-dim-weight-impact/): Choose the right shipping box in 2026: step-by-step guide, DIM weight impact, dunnage rules, USPS Cubic eligibility, and the 3-5 box strategy.
- [How to Reduce Package Size – Design, Procurement, and Bundling](https://dimmath.com/blog/how-to-reduce-package-size/): Reduce package size in 2026: custom box procurement, retail packaging redesign, compression, bundling, and 3PL storage optimization to cut shipping costs.
- [DIM Weight Divisors by Carrier 2026 (Full Table)](https://dimmath.com/blog/dim-weight-divisors-by-carrier-full-table/): DIM divisors 2026: USPS 139 (DMM 283), FedEx 139 US/Intl, UPS 139 commercial domestic. Full carrier table with exceptions.
- [Dimensional Weight vs Actual Weight – When Each Applies](https://dimmath.com/blog/dimensional-weight-vs-actual-weight-when-each-applies/): Dimensional weight vs actual weight — carriers bill whichever is higher. Learn when each applies, how ceiling rounding changed the math, and how to pay less.
- [How to Calculate DIM Weight – Complete Guide](https://dimmath.com/blog/how-to-calculate-dim-weight-complete-guide/): Learn the DIM weight formula for UPS, FedEx, and USPS. See how the 2026 rounding rule affects your billable weight and find the cheapest carrier.
- [How to Reduce DIM Weight – 6 Packaging Tactics That Work](https://dimmath.com/blog/how-to-reduce-dim-weight-6-packaging-tactics-that-save-real-money/): Reduce dimensional weight charges with 6 proven packaging tactics. Right-size boxes, switch mailers, and unlock USPS Cubic to cut shipping costs in 2026.
- [UPS vs FedEx DIM Weight – Who Wins by Zone](https://dimmath.com/blog/ups-vs-fedex-dim-weight-who-wins-by-zone/): UPS and FedEx both use a 139 DIM divisor. See who wins by zone, weight, and package type — plus the USPS change hitting July 12.
- [What is Billable Weight? DIM Rounding Rules Explained](https://dimmath.com/blog/what-is-billable-weight-dim-rounding-rules-explained/): Billable weight is what carriers actually charge you — the higher of actual or DIM weight. Learn how ceiling rounding changed the math and how to pay less in 2026.

### Amazon FBA Fees

- [How to Avoid the FBA Low Inventory and Aged Inventory Fees](https://dimmath.com/blog/how-to-avoid-the-fba-low-inventory-and-aged-inventory-fees/): Amazon charges one fee when stock drops below 28 days and another at 181 days. The sweet spot is 30 to 45 days. Here is the formula.
- [Amazon Returns – The True Cost and Net Margin After Returns](https://dimmath.com/blog/amazon-returns-the-true-cost-and-net-margin-after-returns/): Amazon keeps 20% of your referral fee on every return. The outbound FBA fee is gone.
- [Amazon AWD Costs & When It Saves FBA Sellers Money](https://dimmath.com/blog/amazon-awd-what-it-costs-and-when-it-saves-fba-sellers-money/): Amazon AWD stores bulk inventory below FBA rates. Here is what it costs in 2026, how auto-replenishment works, and when it makes sense.
- [FBA Overmax Fee: Size Thresholds & How to Avoid It](https://dimmath.com/blog/fba-overmax-handling-fee-what-triggers-it-and-how-to-avoid/): Amazon added a $17 to $25 Overmax surcharge in 2026 for Extra-Large products over 96 inches or 130 inches length plus girth. Here is how to avoid it.
- [FBA Returns Processing Fee: Thresholds & Reductions](https://dimmath.com/blog/fba-returns-processing-fee-thresholds-and-how-to-reduce/): FBA returns processing fee applies when your return rate exceeds category threshold. Apparel pays on every return. Here is how to check and reduce yours.
- [FBA IPI Score: Causes, Penalties & How to Fix It](https://dimmath.com/blog/fba-ipi-score-what-drops-it-what-it-costs-and-how-to-fix-it/): FBA IPI below 400 triggers storage limits that block Q4 inventory. Here is what moves the score and how fast recovery takes.
- [FBA Reimbursement Claims: What Amazon Owes You](https://dimmath.com/blog/fba-reimbursement-claims-what-amazon-owes-you/): FBA sellers leave $1,500 to $3,000 unclaimed yearly. Lost inventory, fee overcharges, missing returns. Claim it before the 60-day window closes.
- [How to Drop an FBA Size Tier – The Packaging Audit](https://dimmath.com/blog/how-to-drop-an-fba-size-tier-the-packaging-audit-that-saves-1-to-3-per-unit/): Reducing FBA packaging by half an inch can drop a size tier and save $1 to $3 per unit. Here is the audit process, savings calculation, and thresholds.
- [FBA Reorder Point Formula – Storage vs Low Inventory Fees](https://dimmath.com/blog/fba-reorder-point-formula-storage-vs-low-inventory-fees/): FBA reorder point formula and safety stock sweet spot. How to stay between the storage fee ceiling and low inventory fee floor.
- [Amazon SIPP: Save $2.07/Unit – Eligibility & Enrollment](https://dimmath.com/blog/what-is-amazon-sipp-and-how-to-enroll-fee-savings-guide/): Amazon SIPP lets FBA sellers ship in original packaging. Non-enrolled bulky sellers pay $2.07 per unit extra. Here is who qualifies and how.
- [FBA Shipment Defect Fees: Triggers & Exact Penalties](https://dimmath.com/blog/fba-shipment-defect-fees-what-triggers-them-and-how-to-avoid-a-margin-wipeout/): FBA shipment defect fees hit $0.32 to $5.72 per unit in 2026. One mislabeled pallet wipes out a month of profit. Here is what triggers them.
- [FBA DIM Weight for Bulky Products: Who Pays More](https://dimmath.com/blog/fba-dimensional-weight-for-lightweight-bulky-products-who-gets-hit/): Amazon extended DIM weight to all FBA size tiers in 2026. Yoga mats, pillows, and storage bins now bill at 5 to 10x actual weight
- [FBA Low Inventory Fee – FNSKU Change and Multi-Variant Fix](https://dimmath.com/blog/fba-low-inventory-level-fee-how-the-fnsku-change-affects-multi-variant-sellers/): FBA low inventory fee now hits at FNSKU level not parent ASIN. One low-stock variant triggers fees. Here is what changed and how to fix it.
- [FBA Dimensional Weight for Flat Products – 2-Inch Minimum](https://dimmath.com/blog/fba-dimensional-weight-for-flat-products-the-2-inch-minimum-rule/): Amazon applies a 2-inch minimum to flat oversize products when calculating DIM weight. A 0.5-inch thick item bills as 2 inches.
- [How to Build FBA Fee Increases Into Your Pricing Strategy](https://dimmath.com/blog/how-to-build-fba-fee-increases-into-your-pricing-strategy/): FBA fees increase every year. Build a pricing buffer, stress test new products, optimize price thresholds, and stop scrambling after increases.
- [FBA Inbound Placement: Minimal vs Optimized Split](https://dimmath.com/blog/fba-inbound-placement-fee-minimal-vs-optimized-split-guide/): FBA inbound placement fee explained: minimal vs optimized split, the break-even formula, when each option wins, and the 5 carton requirement.
- [FBA Fees on Oversize Items: When FBA Stops Working](https://dimmath.com/blog/fba-fees-on-oversize-products-when-fba-stops-making-sense/): FBA fees on oversize products Small Bulky, Large Bulky, Overmax surcharge, SIPP program, inbound placement, and when 3PL FBM beats FBA on the same product.
- [How to Reduce FBA Inbound Shipping Cost Per Unit](https://dimmath.com/blog/how-to-reduce-fba-inbound-shipping-cost-per-unit-batch-box-carrier/): FBA inbound shipping costs too high per unit? Fix it with batch consolidation, box weight targets, SPD vs LTL thresholds & the partnered carrier program.
- [Is Amazon FBA Worth It in 2026? Break-Even by Category](https://dimmath.com/blog/is-amazon-fba-worth-it-profit-calculator-decision-framework/): Is Amazon FBA worth it : Full fee stack, GO/NO-GO framework, 3 product profiles with real dollar math, exit signals, and when FBA clearly wins or loses.
- [Amazon Size Tiers – Small, Large, Oversize Full Chart](https://dimmath.com/blog/amazon-fba-size-tiers-smalllargeoversize-full-chart/): Amazon FBA size tiers explained: small standard, large standard, small bulky, and oversize. Full chart with dimensions, weights, and fee differences.
- [Amazon Referral Fee Calculator – Category Breakdown](https://dimmath.com/blog/amazon-referral-fee-calculator-category-breakdown/): Amazon referral fees by category : full rate table, tiered categories explained, minimum fee impact, pricing floor formula & how to calculate true margin.
- [FBA Long-Term Storage Fees – How to Avoid it](https://dimmath.com/blog/fba-long-term-storage-fees-how-to-avoid-it/): FBA aged inventory surcharge starts at 181 days in 2026: $1.25 to $6.90 per cubic foot. How to avoid fees, when to remove, and the 14th deadline.
- [FBA vs FBM – Profit Comparison](https://dimmath.com/blog/fba-vs-fbm-profit-comparison/): FBA vs FBM 2026: full cost formula, real dollar comparison, when FBM wins, hybrid strategy by SKU, and the low inventory fee exemption for FBM.
- [How to Lower FBA Fees – 7 Tactics That Work](https://dimmath.com/blog/how-to-lower-fba-fees-7-tactics-that-work/): Cut shipping costs and protect FBA margins in 2026 with 7 proven tactics every seller should know.
- [FBA Box Limits 2026: 36×25×25 in, 50 lb, ECT-32](https://dimmath.com/blog/fba-box-requirements-carton-limits-weight-labeling/): FBA box requirements 2026: 36x25x25 inch max, 50 lb limit, ECT-32 standard, Team Lift rules, FNSKU labeling, and inbound defect fees up 10x.
- [FBA Inbound Shipping: Partnered Rates & Box Limits](https://dimmath.com/blog/fba-inbound-shipping-partnered-carrier-rates-box-limits/): FBA inbound shipping: partnered carrier rates, SPD vs LTL, box limits, DIM weight, placement fee options, and Q4 timing strategy
- [FBA Referral Fees by Category – Full Table ](https://dimmath.com/blog/fba-referral-fees-by-category-full-table/): Amazon referral fees by category in 2026: 8% to 45% full table, tiered rates explained, minimum fee impact, and how category choice affects your margin floor.
- [FBA Small Standard vs Large Standard – Size Tier Thresholds](https://dimmath.com/blog/fba-small-standard-vs-large-standard-size-tier-thresholds/): FBA size tiers 2026: small standard vs large standard thresholds, fee differences, new Small Bulky tier, and how the right tier protects your margin.
- [Amazon FBA Fees 2026: Every Fee, With Real Numbers](https://dimmath.com/blog/amazon-fba-fees-explained-complete-breakdown/): Every Amazon FBA fee in 2026: referral, fulfillment, storage, placement, fuel surcharge. Check your true margin before ordering inventory.
- [FBA Fee Changes 2026: What Changed & Who Got Hit](https://dimmath.com/blog/fba-fee-changes-what-changed-who-got-hit/): Amazon 2026 FBA fee changes: peak fees, permanent increases, FBA Prep ended, and low inventory threshold shift. See who got hit hardest.
- [FBA Profit Margin Benchmarks by Category](https://dimmath.com/blog/fba-profit-margin-benchmarks-by-category/): What is a good FBA profit margin? Benchmarks by category, GO/NO-GO thresholds, and how fee increases shifted margins across 10 categories.
- [How to Calculate FBA Profit – COGS, Fees, Break-Even](https://dimmath.com/blog/how-to-calculate-fba-profit-cogs-fees-break-even-walkthrough/): Step-by-step FBA profit calculation including COGS, referral fees, fulfillment, fuel surcharge, and PPC. Find your break-even price and GO/NO-GO margin in 2026

### Carrier Comparison

- [Shopify Shipping Rates: Stop Overpaying on Every Label](https://dimmath.com/blog/shopify-shipping-rates-how-to-stop-overpaying-on-every-label/): Shopify Shipping gives up to 88% off carrier rates but misses USPS Cubic. Here is how to set it up and save more on every label.
- [Which Shipping Carrier Is Cheapest? Updated Monthly Analysis | DimMath](https://dimmath.com/blog/which-shipping-carrier-is-cheapest-updated-monthly-analysis/): Monthly UPS, FedEx, USPS Ground Advantage, and USPS Cubic benchmark hub. September 2026 is the current issue. Not live quotes.
- [Why Shopify UPS Rates Are Wrong – How to Fix the Discrepancy](https://dimmath.com/blog/why-shopify-ups-rates-are-wrong-how-to-fix-the-discrepancy/): Shopify UPS rates wrong at checkout? Four causes explained: retail vs commercial, dimension mismatch, hidden surcharges, and international inflation.
- [Shopify Shipping Rates Explained – Carrier Accounts and Discounts](https://dimmath.com/blog/shopify-shipping-rates-explained-carrier-accounts-and-discounts/): Shopify shipping rates i: flat rates, calculated carrier rates, Shopify Shipping discounts up to 88%, FedEx exclusion, DIM weight & free shipping math
- [Best Shipping Software for Shopify – Free and Paid](https://dimmath.com/blog/best-shipping-software-for-shopify-free-and-paid/): Best Shopify shipping software 2026: Shopify built-in, Veeqo, Pirate Ship, Shippo, and ShipStation compared by price, carriers, and volume.
- [Cheapest Carrier by Zone 2026: Zone 2-8 Price Table](https://dimmath.com/blog/cheapest-carrier-by-zone-zone-2-8-price-comparison-table/): Cheapest carrier by zone 2026: USPS wins Zones 2-4 under 5 lbs. UPS and FedEx win Zones 6-8 above 10 lbs. Full rate table included.
- [FedEx vs USPS – When to Use Each ](https://dimmath.com/blog/fedex-vs-usps-when-to-use-each/): FedEx vs USPS 2026: USPS wins under 2 lbs and residential deliveries. FedEx wins on weekend coverage, tracking, and heavy packages.
- [Pirate Ship vs ShipStation vs Shippo – Full 2026 Comparison](https://dimmath.com/blog/pirate-ship-vs-shipstation-vs-shippo-comparison/): Pirate Ship vs ShipStation vs Shippo 2026 comparison: monthly pricing, per-label fees, USPS Cubic access, carrier discounts, and which software fits your volume.
- [UPS vs FedEx Ground – Rates Speed DIM Who Wins](https://dimmath.com/blog/ups-vs-fedex-ground-rates-speed-dim-who-wins/): UPS vs FedEx Ground 2026: same 5.9% increase, same DIM divisor 139. Differences are surcharges, speed, economy tiers, and negotiated rates
- [UPS vs USPS – E-commerce Seller Guide](https://dimmath.com/blog/ups-vs-usps-e-commerce-seller-guide/): UPS vs USPS: USPS wins under 2 lbs and all residential deliveries. UPS wins above 10 lbs commercial. July 12 shifts the comparison.
- [Cheapest Way to Ship Small Packages in 2026 (Compared)](https://dimmath.com/blog/cheapest-way-to-ship-small-packages-usps-vs-ups-vs-fedex/): Cheapest carrier for small packages in 2026 by weight and zone. USPS wins under 1 lb. USPS Cubic beats all for dense packages
- [UPS FedEx USPS Rate Increases – What They Actually Cost You](https://dimmath.com/blog/carrier-rate-increases-what-ups-fedex-usps-actually-cost-you-now/): Carrier rate increases explained. UPS, FedEx, and USPS raised rates 5.9-7.8%. See what your shipping actually costs now and how to pay less.

### USPS Cubic & Ground Advantage

- [Why USPS Rates Are Different on eBay, Pirate Ship, and USPS.com](https://dimmath.com/blog/why-usps-rates-are-different-on-ebay-pirate-ship-and-uspscom/): USPS has three rate tiers. The platform you use determines which one you get. Here is why each platform shows a different price
- [Why USPS Cubic Pricing Is Not Showing at Shopify Checkout](https://dimmath.com/blog/why-usps-cubic-pricing-is-not-showing-at-shopify-checkout/): USPS Cubic not showing at Shopify checkout? It is not available natively. Here is why, which apps fix it, and a free workaround.
- [How to Qualify for USPS Cubic: Rules & Limits](https://dimmath.com/blog/how-to-qualify-for-usps-cubic-22-inch-max-20-lb-max/): USPS Cubic eligibility 2026: 22 inch max, 20 lb max, volume limits, commercial rate access, and the July 12 dimension compliance rule explained.
- [USPS Cubic Tier Pricing – Full Rate Table](https://dimmath.com/blog/usps-cubic-tier-pricing-full-rate-table/): USPS Cubic tier pricing: 5 Priority Mail tiers and 10 Ground Advantage tiers with rates by zone, box dimension examples, and tier breakpoint optimization.
- [USPS Ground Advantage vs Ground Advantage Cubic: 2026 Table](https://dimmath.com/blog/usps-cubic-vs-ground-advantage-when-cubic-wins/): Compare USPS Ground Advantage vs Cubic rates by zone. See 10-tier cubic table, size limits (1 cu ft, 20lb) & when cubic is 20-60% cheaper. With cost examples.
- [USPS Flat Rate Box Sizes 2026: Dimensions & Prices](https://dimmath.com/blog/usps-flat-rate-box-sizes-dimensions-costs-when-to-use/): USPS Flat Rate box sizes and 2026 prices: Small $11.20, Medium $19.60, Large $28.70 commercial. DIM exempt, nonstandard fee exempt. When flat rate wins and when it loses.
- [USPS Ground Advantage Rates 2026 – Zone Chart & Weight Breaks](https://dimmath.com/blog/usps-ground-advantage-rates-zone-chart-weight-breaks/): USPS Ground Advantage commercial rates by zone and weight. Notice 123 tables effective July 12, 2026.

### International, Duty & Landed Cost

- [How to Ship a Kayak – LTL Freight Options, Costs and Packing Steps](https://dimmath.com/blog/how-to-ship-a-kayak-ltl-freight-options-costs-and-packing-steps/): Most kayaks exceed UPS and FedEx max length. LTL freight is the answer. Here is the cost by kayak type and how to pack for transit.
- [De Minimis Suspended: How Ecommerce Sellers Adapt](https://dimmath.com/blog/de-minimis-suspended-how-ecommerce-sellers-adapt-and-profit/): The $800 de minimis threshold is gone. Every import now pays duty and MPF. Here is what ecommerce sellers do to stay profitable.
- [LTL Freight Class Explained: Density & Tier Formula](https://dimmath.com/blog/ltl-freight-class-explained-how-to-calculate-and-why-it-matters/): LTL freight class sets your rate on every pallet. The NMFC changed in July 2025. Here is how density now drives your shipping cost.
- [How the Strait of Hormuz Crisis Is Raising Your Import Costs](https://dimmath.com/blog/how-the-strait-of-hormuz-crisis-is-raising-your-import-costs/): The Strait of Hormuz has been closed since February 2026. Here is what it means for freight costs, lead times, and your margins
- [DHL vs FedEx International: Which Carrier Is Cheaper](https://dimmath.com/blog/dhl-vs-fedex-international-shipping-which-carrier-is-cheaper/): DHL is cheaper for international shipments. FedEx wins domestically. The right choice depends on weight, route, and service tier.
- [Air vs Ocean Freight: Cost, Speed & When to Switch](https://dimmath.com/blog/air-freight-vs-ocean-freight-cost-speed-and-when-to-switch/): Air freight costs 4 to 15 times more than ocean. Here is the break-even formula and decision framework for every shipment type.
- [Is De Minimis Coming Back? July 24 Update](https://dimmath.com/blog/is-de-minimis-coming-back-july-24-update-and-what-sellers-need-to-know/): De minimis is not coming back. CBP made it permanent June 24 2026. July 24 closes the postal loophole. Act before October 22.
- [How to Fix Your Dropshipping Model After De Minimis Ended](https://dimmath.com/blog/how-to-fix-your-dropshipping-model-after-de-minimis-ended/): De minimis is gone & the direct-from-China parcel model is broken. The US warehouse pivot that fixes it: bulk import, clear once, fulfill domestically.
- [How to Rebuild Your Margins After China Tariffs](https://dimmath.com/blog/how-to-rebuild-your-margins-after-china-tariffs/): China tariffs collapsed your margins? Recalculate landed cost, verify your HTS code, triage SKUs, test price increases gradually & use FBM as a margin lever.
- [DDP Shipping from Supplier – What It Covers and Does Not](https://dimmath.com/blog/ddp-shipping-from-supplier-what-it-covers-and-what-it-does-not/): DDP shipping from a supplier: what Delivered Duty Paid covers, the named place problem, FOB confusion, and how to protect yourself.
- [International Shipping for Small Stores – DDP vs DDU](https://dimmath.com/blog/international-shipping-for-small-stores-ddp-vs-ddu/): DDP vs DDU international shipping : who pays duties, EU July 2026 de minimis end, refusal rate math, conversion lift from DDP, and when DDU still makes sense.
- [How to Calculate Landed Cost – Complete Formula ](https://dimmath.com/blog/how-to-calculate-landed-cost-complete-formula/): Landed cost formula 2026: product cost, freight, insurance, duty on CIF value, MPF, HMF, and broker fees. Per unit cost and margin check.
- [HS Code Finder Guide – How to Classify, HTS Lookup Walkthrough](https://dimmath.com/blog/hs-code-finder-guide-how-to-classify-hts-lookup-walkthrough/): How to find your HS & HTS code in 2026: USITC lookup walkthrough, 10-digit structure explained, supplier verification & cost of errors
- [MPF and HMF Fees Explained – 0.3464%, Min/Max, When Each Applies](https://dimmath.com/blog/mpf-and-hmf-fees-explained-03464-minmax-when-each-applies/): MPF is 0.3464% of customs value, min $33.58, max $651.50. HMF is 0.125% ocean only. 2026 rates, exemptions, and consolidation strategy.
- [Section 321 De Minimis $800 – How It Works, Who Qualifies](https://dimmath.com/blog/section-321-de-minimis-800-how-it-works-who-qualifies/): Section 321 de minimis $800 suspended in 2026. What changed, who qualifies, shipment costs now, and what sellers who relied on it must do.

### Marketplace Fees

- [How Amazon FBA Sellers Are Building Revenue Streams Off Amazon](https://dimmath.com/blog/how-amazon-fba-sellers-are-building-revenue-streams-off-amazon/): Amazon owns your customers. FBA sellers building on TikTok Shop and Meta ads stop depending on one platform for all their revenue.
- [Depop Fees Explained: Zero Commission & Real Costs](https://dimmath.com/blog/depop-fees-explained-zero-commission-and-what-you-still-pay/): Depop charges 0% selling fee in the US and UK. You pay 3.3% plus $0.45 per sale. Boosted Listings jumped to 12% in March 2026.
- [TikTok Shop Seller Fees Explained – The True Cost of Selling](https://dimmath.com/blog/tiktok-shop-seller-fees-explained-the-true-cost-of-selling/): TikTok Shop raised its referral fee to 8% on August 4 2026. Add affiliates and ads and the real cost hits 35 to 55 percent of GMV.
- [Walmart Marketplace Fees Explained – What Sellers Actually Pay](https://dimmath.com/blog/walmart-marketplace-fees-explained-what-sellers-actually-pay/): Walmart charges no monthly fee. You pay 6 to 15% referral plus WFS if you use fulfillment. Here is every fee explained.
- [Etsy Seller Fees Explained: The True Cost of Selling](https://dimmath.com/blog/etsy-seller-fees-explained-the-true-cost-of-selling-on-etsy/): Etsy takes 10 to 12 percent on every sale before ads. Here is every fee explained with real examples so you can price for profit.
- [eBay Fees Explained: What Sellers Pay Per Transaction](https://dimmath.com/blog/ebay-fees-explained-what-sellers-actually-pay-per-transaction/): eBay takes 13.6% on every sale including shipping. Here is every fee with real examples so you can price for profit on every listing.

### Shipping Cost Strategy

- [How to Dispute a Carrier Billing Adjustment and Get Money Back](https://dimmath.com/blog/how-to-dispute-a-carrier-billing-adjustment-and-get-money-back/): UPS gives you 180 days. FedEx gives you 60. Here is the process and evidence that wins billing adjustments back from each carrier.
- [How to Ship Golf Clubs – Carrier Options, Costs and Packing Steps](https://dimmath.com/blog/how-to-ship-golf-clubs-carrier-options-costs-and-packing-steps/): Golf club boxes trigger Additional Handling on UPS and FedEx. Here is which carrier wins and how to pack clubs without damage.
- [How to Ship a Large TV – Size, Surcharges and Carrier Options](https://dimmath.com/blog/how-to-ship-a-large-tv-size-surcharges-and-carrier-options/): A 65-inch TV triggers the Large Package Surcharge on UPS and FedEx. Here is the cost by size and how to avoid the overcharges.
- [How to Ship a Bike – Carrier Options, Costs and Packing Steps](https://dimmath.com/blog/how-to-ship-a-bike-carrier-options-costs-and-packing-steps/): A boxed bike bills at 109 lbs DIM weight regardless of actual weight. Here is the right carrier, box size, and packing steps.
- [Cheapest Shipping by Carrier — September 2026 Benchmark Issue | DimMath](https://dimmath.com/blog/cheapest-shipping-september-2026/): September 2026 DimMath carrier benchmark: fixed package set across UPS, FedEx, USPS Ground Advantage, and Cubic. Rerun, not a new rate table.
- [How to Read a UPS or FedEx Shipping Invoice – Every Line Item](https://dimmath.com/blog/how-to-read-a-ups-or-fedex-shipping-invoice-every-line-item/): UPS and FedEx add post-delivery charges most sellers never see coming. Here is what every line item on your invoice actually means.
- [The True Cost of Shipping One Order – And How to Calculate It](https://dimmath.com/blog/the-true-cost-of-shipping-one-order-and-how-to-calculate-it/): The label is not your true shipping cost. Add packaging, labor, surcharges, and returns and you are paying 30 to 53 percent more.
- [What Is a Delivery Area Surcharge and How to Avoid It](https://dimmath.com/blog/what-is-a-delivery-area-surcharge-and-how-to-avoid-it/): UPS and FedEx charge up to $16.75 per package for remote ZIP codes. USPS never does. Here is what triggers it and how to avoid it.
- [What Is a Fuel Surcharge and How Do UPS and FedEx Calculate It](https://dimmath.com/blog/what-is-a-fuel-surcharge-and-how-do-ups-and-fedex-calculate-it/): UPS and FedEx add a weekly fuel surcharge to every shipment. At 25 to 27 percent of base rate it adds up to thousands per month.
- [How to Ship a Couch: Cost, Carriers, and the Hidden Fees](https://dimmath.com/blog/how-to-ship-a-couch-cost-carriers-and-the-hidden-fees/): Shipping a couch costs $180-$1,200. Here's how to pick the right carrier, avoid the accessorial trap, and save on LTL freight.
- [How to Ship a Treadmill: Freight Class, Cost, Fold Rule](https://dimmath.com/blog/how-to-ship-a-treadmill-freight-class-cost-fold-rule/): Treadmill shipping costs $385-$1,095. No parcel carrier accepts them. The fold rule changes your freight class and your bill before you book.
- [How to Ship a Mattress – Every Carrier Option and Real Costs](https://dimmath.com/blog/how-to-ship-a-mattress-every-carrier-option-and-real-costs/): Memory foam mattress: use UPS or FedEx compressed. Innerspring: use LTL freight. Here is the cost by size and the packing steps.
- [Cheapest Shipping by Carrier — August 2026 Benchmark Issue | DimMath](https://dimmath.com/blog/cheapest-shipping-august-2026/): Archived August 2026 DimMath carrier benchmark. USPS, UPS, FedEx, and Cubic by weight, zone, DIM, and residential surcharge. Not live quotes.
- [Zone Skipping – How Smart Sellers Cut Shipping Costs by Zone](https://dimmath.com/blog/zone-skipping-how-smart-sellers-cut-shipping-costs-by-zone/): Zone skipping saves $3 to $7 per package on high-zone lanes. Here is how sellers use it and when the volume justifies it.
- [How Ecommerce Sellers Run Their Own Meta Ads Without an Agency](https://dimmath.com/blog/how-ecommerce-sellers-run-their-own-meta-ads-without-an-agency/): Agency fees start at 15% of ad spend. Most ecommerce sellers cannot afford that. Here is how to run Meta ads profitably yourself
- [Do Ecommerce Sellers Need an LLC & When to Get One](https://dimmath.com/blog/do-ecommerce-sellers-need-an-llc-and-when-should-you-get-one/): No platform requires an LLC to start. But as revenue grows your personal assets are at risk. Here is when forming one makes sense.
- [Why Your Shipping Costs Keep Rising Even With the Same Rates](https://dimmath.com/blog/why-your-shipping-costs-keep-rising-even-with-the-same-rates/): Your carrier rates stayed the same but your shipping bill keeps climbing. Six reasons why and what to check on every shipment.
- [How to Avoid UPS and FedEx Package Adjustment Fees](https://dimmath.com/blog/how-to-avoid-ups-and-fedex-package-adjustment-fees/): UPS and FedEx adjustment fees appear weeks after delivery. Most start at the packing station. Here is what triggers them.
- [Shipping Estimator vs Live Quote: Key Differences](https://dimmath.com/blog/shipping-rate-calculator-vs-live-quote-what-each-tells-you/): A shipping calculator gives a planning estimate. A live quote gives the label price. Here is what each shows and when to use which.
- [UPS and FedEx Money-Back Guarantee – Claim Late Delivery Refunds](https://dimmath.com/blog/ups-and-fedex-money-back-guarantee-claim-late-delivery-refunds/): UPS and FedEx refund late deliveries in full. One minute late qualifies. File within 15 days or lose the refund permanently.
- [What Percentage of Revenue Should Shipping Cost?](https://dimmath.com/blog/what-percentage-of-revenue-should-shipping-cost/): Most stores track total shipping spend but miss where it leaks. Here is the per-SKU per-route audit that finds the products killing your margin.
- [How to Negotiate Rates With UPS & FedEx](https://dimmath.com/blog/how-to-negotiate-carrier-rates-with-ups-and-fedex/): UPS and FedEx negotiate with sellers shipping 200 plus packages weekly. Ask for surcharge caps and GRI protection not just base rate discounts.
- [Shipping Insurance vs Declared Value – When to Buy](https://dimmath.com/blog/shipping-insurance-vs-declared-value-when-to-buy/): UPS and FedEx declared value is not insurance. USPS is. Third-party costs 40 to 60 percent less. Here is when to buy coverage and when to skip
- [How to Calculate Your Free Shipping Threshold](https://dimmath.com/blog/how-to-calculate-your-free-shipping-threshold/): Most stores set free shipping by gut feel and lose money. Here is the formula using all-in shipping cost and zone weighting to find the right number.
- [Why Your Shipping Cost Is Higher Than the Label](https://dimmath.com/blog/why-your-shipping-cost-is-higher-than-the-label/): Carrier label shows one price. Invoice shows another. Here's why: duties, broker fees, disbursement charges & surcharges carriers do not show at checkout
- [Additional Handling Surcharge 2026: UPS & FedEx Thresholds](https://dimmath.com/blog/ups-and-fedex-additional-handling-surcharge/): UPS and FedEx additional handling surcharge: new cubic volume thresholds, ceiling rounding, 40 lb minimum, and how to avoid the fees.
- [How to Reduce Shipping Costs – 12 Tactics That Work i](https://dimmath.com/blog/how-to-reduce-shipping-costs-12-tactics-that-work/): 12 tactics to reduce ecommerce shipping costs : DIM weight, USPS Cubic, multi-carrier, negotiation, zone reduction, address validation, invoice audit
- [Shipping Insurance – When to Buy, Carriers Compared](https://dimmath.com/blog/shipping-insurance-when-to-buy-carriers-compared/): Carrier declared value vs third-party insurance: rates compared, break-even formula for coverage, and claim documentation for UPS, FedEx, and USPS.
- [How to Offer Free Shipping Profitably – Threshold Math ](https://dimmath.com/blog/how-to-offer-free-shipping-profitably-threshold-math/): How to offer free shipping profitably: threshold formula, full landed cost, modal vs mean AOV, price rolling, regional thresholds, and A/B test framework.
- [Shipping Zones Explained: How Zones & Skipping Work](https://dimmath.com/blog/shipping-zones-explained-how-zones-work-and-zone-skipping/): Shipping zones explained: how zones are calculated, dollar cost by zone, zone lookup, and how zone skipping cuts shipping costs up to 30%.

## Rate Data

- [Full rate dump (llms-full.txt)](https://dimmath.com/llms-full.txt): Inline markdown tables and the 10 primary guides, generated from the same content collections as the HTML pages.
- [Open Rate Data](https://dimmath.com/data/): Public downloadable CSV and JSON dataset snapshots for DIM weight divisors, carrier surcharge triggers, and USPS cubic tiers.
- [Rate Changelog](https://dimmath.com/changelog/): Log of recorded calculator and table updates. Not every entry cites a source document. Official publications on the homepage are references for checking estimates, not proof that every displayed number was audited.