FBA Reorder Point Formula – Storage vs Low Inventory Fees

In 2026 FBA sellers are caught between two fees pulling in opposite directions.

Hold too little stock and the low inventory level fee charges you on every sale when historical days of supply drops below 28 days. Hold too much stock and aged inventory surcharges hit at 181 days, 90 days earlier than the old threshold.

The sellers who avoid both fees are not guessing. They are using a reorder point formula calibrated to FBA’s specific lead time components and sizing their safety stock to live inside the gap between the fee floor and the fee ceiling.

This guide explains the formula, the inputs that make it accurate for FBA specifically, and the safety stock range that keeps you out of both fee zones simultaneously.

The Two-Fee Trap – Floor and Ceiling

Before running the formula it helps to understand the structural problem it solves.

The floor: Low inventory level fee.
When your historical days of supply at the FNSKU level drops below 28 days, Amazon charges a per-unit low inventory level fee on every sale. The fee has three tiers based on how far below 28 days your supply falls: 0 to 14 days, 14 to 21 days, and 21 to 28 days. The lower your days of supply, the higher the fee per unit. Verify the current per-unit amounts for your size tier in Seller Central under the low inventory level fee help page. The fee applies only to FNSKUs that have sold 20 or more units in the past 7 days.

This fee creates a hard floor under your inventory. You must maintain at least 28 days of historical supply on every active FNSKU or you pay a recurring per-unit penalty on every sale.

The ceiling: Aged inventory surcharge.
When inventory has been in Amazon’s fulfillment centers for 181 days or more, aged inventory surcharges apply. The surcharge threshold dropped from 271 days to 181 days in 2026, giving sellers 90 fewer days of runway before aged inventory fees kick in.

This creates a hard ceiling above your inventory. You cannot hold more stock than you can sell in approximately 150 days before the surcharge window opens, accounting for the time already elapsed since the shipment arrived.

The gap between floor and ceiling is where optimal inventory lives.
At least 28 days of supply to stay above the floor. No more than approximately 150 days of supply at current velocity to stay below the ceiling. The reorder point formula and safety stock calculation keep you in that range on every SKU.

For the complete breakdown of aged inventory surcharge rates and removal timing, see FBA Long Term Storage Fees.

The Reorder Point Formula – FBA Version

The standard reorder point formula is:

Reorder Point = (Daily Velocity × Lead Time Days) + Safety Stock

For FBA specifically, two inputs require adjustment that most sellers get wrong.

Input 1: Daily Velocity – Which Window to Use

Daily velocity is your average units sold per day. The window you use to calculate it matters.

For fast-moving SKUs (20 or more units sold per week): use your trailing 30-day velocity. Fast-moving products can change velocity quickly. A 30-day window reflects current demand more accurately than a longer period.

For slow-moving SKUs (fewer than 20 units per week): use your trailing 90-day velocity. Slow-moving products have more day-to-day variance. A 90-day window smooths out the noise and produces a more reliable average.

Never mix the windows across your catalog. Fast-moving SKUs on a 90-day window underreact to velocity increases. Slow-moving SKUs on a 30-day window overreact to short-term spikes.

Input 2: FBA Lead Time – The Component Most Sellers Undercount

FBA lead time is not just the transit time from your supplier to the US port. It is the full chain:

Manufacturing time: how long it takes your supplier to produce the order after payment is confirmed. For made-to-order products this can be 2 to 4 weeks. For products made from existing components it may be 1 to 2 weeks.

Ocean freight transit: typically 3 to 5 weeks from China to a US port depending on origin and destination.

Port and customs clearance: 3 to 7 days typically, longer during peak seasons or if your shipment is selected for inspection.

Inland freight from port to prep center or directly to Amazon: 3 to 7 days depending on destination FC location.

FBA receiving time: the time between your shipment arriving at the Amazon fulfillment center and the inventory becoming available for sale. This step adds 7 to 14 days and is the component most sellers forget to include in their lead time calculation.

Total FBA lead time from order to available status at the Amazon fulfillment center typically ranges from 45 to 75 days.

FAQ

Q: What is the reorder point formula for Amazon FBA?
A: The FBA reorder point formula is: Reorder Point = (Daily Velocity × Lead Time Days) + Safety Stock. For FBA specifically, lead time must include all components: manufacturing time, ocean freight transit, port and customs clearance, inland freight, and FBA receiving time. FBA receiving time alone adds 7 to 14 days beyond FC arrival that most sellers forget to include. Total China to FBA lead time is typically 56 to 84 days. Use trailing 30-day velocity for fast-moving SKUs and trailing 90-day velocity for slow-moving SKUs. Use the FBA Fee Calculator to model how different inventory levels affect your total per-unit cost including storage fees.

Q: How much safety stock should I hold for FBA in 2026?
A: The 2026 safety stock sweet spot is 30 to 45 days of average sales. This range keeps you above the 28-day low inventory level fee floor while staying well below the 181-day aged inventory surcharge ceiling. Size safety stock using the max-minus-average method: Maximum Daily Velocity minus Average Daily Velocity, multiplied by Maximum Lead Time Days. Calculate safety stock per FNSKU using each variant’s individual velocity, not the parent product’s combined velocity, because the low inventory level fee calculates at the FNSKU level since January 2026.

Q: How do I stay above the 28-day FBA low inventory level fee threshold?
A: Set your reorder point using the full FBA lead time including manufacturing, transit, port clearance, inland freight, and FBA receiving time of 7 to 14 days. Size safety stock to 30 to 45 days of average sales at the FNSKU level. Monitor days of supply weekly in Seller Central FBA Inventory and flag any FNSKU below 35 days immediately. At 35 days you have a 7-day buffer before crossing the 28-day fee threshold. If a FNSKU drops below 35 days and has sold 20 or more units in the past 7 days, place a restock order or convert to FBM temporarily to stop the fee while awaiting new inventory.

Q: How do I avoid FBA aged inventory surcharges while maintaining enough safety stock?
A: The aged inventory surcharge now starts at 181 days in 2026, down from 271 days in 2025. Monitor storage age weekly and initiate removals or liquidations on any inventory at 150 or more days before the surcharge triggers. Size safety stock to 30 to 45 days rather than the 45 to 60 days many sellers ran before 2026. Consider Amazon Warehousing and Distribution for buffer stock since AWD inventory does not count toward FBA aged inventory thresholds and replenishes FBA automatically. See FBA Long Term Storage Fees for the complete removal timing framework.