Box Size Finder
Input your item dimensions and required padding to find the most efficient box. Compare against standard USPS Flat Rate sizes instantly.
01Item Dimensions
Inches
Standard bubble wrap is ~0.5in. Applied to all 6 sides.
Recommended Container
Large FRB
Available Matches1
Min. Box Length11"
Formula Applied
L:11" x W:9" x H:5"Verified against official carrier fee schedules (2026-06-19)
Flat Rate Box Compatibility
Small FRBToo Large
Medium FRB (Side)Too Large
Medium FRB (Top)Too Large
Large FRBFits
Accounting for Dunnage
Bubble wrap, packing peanuts, and air pillows add volume. Always add at least 0.5" to each side for fragile items.
Flat Rate Savings
If your item fits a Flat Rate box and is heavy, you could save up to 40% vs Priority Mail commercial rates.
Inner vs Outer
Dimensions listed on boxes are usually outer measurements. Our finder calculates required inner clearance.