Free tool
Find out how close you are to a cheaper size tier.
Tier boundaries are cliffs, not slopes. Enter your packaged dimensions and weight — we return the tier, the dimensional weight, the billable weight, and the exact gap on every constraint that is holding you in the tier you are in.
Packaged unit
Measure the unit as it ships — outer packaging included, at its widest points.
US tier limits used
| Tier | Max dimensions | Weight |
|---|---|---|
| Small standard | 15 x 12 x 0.75 in | 16 oz or under |
| Large standard | 18 x 14 x 8 in | 20 lb or under |
| Small bulky | 37 x 28 x 20 in; length + girth ≤ 130 in | 50 lb or under |
| Large bulky | 59 x 33 x 33 in; length + girth ≤ 130 in | 50 lb or under |
| Extra-large | beyond large bulky, or length + girth over 130 in | banded under 50 lb, 50-70 lb, 70-150 lb, over 150 lb |
Dimensions are longest / median / shortest side. Small bulky was introduced January 15, 2026. Verified against published 2026 US schedules in August 2026 — always confirm the final fee in Seller Central's Fee Preview before you commit tooling.
The read
Size tier
—
- —
- unit weight
- —
- dim. weight
- —
- billable
Gap to the next tier down
Operator's verdict
Length + girth = longest side + 2 x (median + shortest). Standard dimensional weight = L x W x H / 139; bulky and extra-large calculations use a 2 in minimum for the median and shortest sides before dividing by 139.
How does Amazon decide my FBA size tier?
By the packaged unit's three dimensions and its unit weight — not by what the product is. Amazon sorts your dimensions into longest, median, and shortest side and checks them against each tier's limits in order. A unit falls into the first tier it fits entirely; failing any single limit pushes it into the next tier up, which is why one oversized side can cost more than extra weight.
What is dimensional weight and when does Amazon use it?
Dimensional weight is length x width x height divided by 139, and it prices the space a unit occupies rather than its mass. For large standard, bulky, and extra-large units up to 150 lb, Amazon bills the greater of unit weight and dimensional weight. Small standard and extra-large over 150 lb use unit weight. A light product in a generous box gets billed for the air.
Is it worth redesigning packaging to drop a size tier?
Almost always, if the gap is small. Tier boundaries are cliffs, not slopes — a fraction of an inch on the shortest side can move a unit between tiers and change the fee for every unit you will ever ship. Run the numbers on tooling and carton cost against annual volume before committing, but check the gap first: most sellers have never measured how close they are.
Put the tier into a complete P&L with the Amazon FBA Profit Calculator · Related reading: Size tiers ·FBA fulfillment fee ·Volumetric weight · or have an operator run the catalog.
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