FBA Fee Calculator

The first time I ran a real FBA fee through Amazon's calculator, the number was higher than I expected and lower than the horror stories I'd read. That's the thing about FBA fees: they're not random, but the table has enough tiers and exceptions that guessing by hand is a good way to lose money on a product you thought was profitable.

This calculator does the part that's annoying to do by hand: it figures out which size tier your unit lands in, decides whether the weight or the dimensional weight gets billed, and applies the right rate. You put in the box dimensions and the shipping weight, and it tells you the fulfillment fee.

Why dimensional weight matters

For most small items, Amazon bills the actual weight. For bulky-but-light things — a foam pillow, a folded tote, a package of party decorations — the dimensional weight is what bites. The formula is length × width × height in inches, divided by 139. If that number is bigger than the scale weight, that's what you pay for.

I've watched sellers price a product correctly for its real weight, then get surprised when a slightly bigger box pushed it into oversize. The box you choose is part of your cost, not just packaging.

Standard vs oversize

The cutoff is 18 × 14 × 8 inches and 20 lb. Cross any one of those and you're in oversize, where the per-pound rate jumps and a handling surcharge can appear. If you're close to the line, shaving an inch off the box or shipping in a smaller master carton can keep you in standard — and the fee difference is often more than the packaging savings you'd get from going bigger.

Apparel surcharge

Clothing carries a small per-unit fee on top of the normal rate. It's easy to forget because it's tiny next to the main fee, but across a few hundred units a month it adds up to real money, and it changes whether a thin-margin shirt is worth listing.

Use it before you source

The most useful time to run this is before you buy inventory, not after. Punch in the dimensions from the supplier's spec sheet, see the fee, subtract it from your planned price along with your cost and the referral fee, and you'll know the margin before you commit. If the number is ugly, you still have time to negotiate a smaller package or pick a different product.

One caveat worth repeating: Amazon revises these rates almost every year, usually in January and sometimes mid-year. The table built into this tool reflects the 2024 US rates. When Amazon announces a change, re-check your worst-margin products first — those are the ones a small fee bump turns red.