Amazon FBA sizing
Find your FBA size tier from dimensions and weight.
Small standard through Extra-Large, with the shipping weight Amazon uses for fees and the reason a smaller tier was ruled out.
Sort the sides, compute dimensional weight (volume ÷ 139), then take the first tier whose weight and size limits all fit. Small standard and Extra-Large 150+ lb use unit weight; every other tier uses the greater of unit and dimensional weight.
Packaged unit
Result
Size tier limits from January 15, 2026
| Tier | Weight | Longest | Median | Shortest | Length + girth |
|---|---|---|---|---|---|
| Small standard-size | Up to 16 oz (unit weight) | 15 in | 12 in | 0.75 in | n/a |
| Large standard-size | Up to 20 lb | 18 in | 14 in | 8 in | n/a |
| Small Bulky | Up to 50 lb | 37 in | 28 in | 20 in | 130 in |
| Large Bulky | Up to 50 lb | 59 in | 33 in | 33 in | 130 in |
| Extra-Large 0 to 50 lb | Up to 50 lb | Over 59 in, or over 33 in median/shortest, or over 130 in length + girth | |||
| Extra-Large 50+ to 70 lb | 50+ to 70 lb | Same dimension limits as above | |||
| Extra-Large 70+ to 150 lb | 70+ to 150 lb | Same dimension limits as above | |||
| Extra-Large 150+ lb | Over 150 lb (unit weight) | Same dimension limits as above |
Girth is 2 × (median side + shortest side), and length plus girth is the longest side plus girth. Dimensional weight is length × width × height ÷ 139; for Small Bulky, Large Bulky, Overmax and Extra-Large units Amazon assumes a minimum width and height of 2 inches. Extra-Large units up to 150 lb with a longest side over 96 inches or length plus girth over 130 inches are Overmax and pay an extra $17 (0 to 50 lb), $21 (50+ to 70 lb) or $25 (70+ to 150 lb).
One conflict in Amazon’s own pages: the dimensional weight page lists a 40 × 1 × 25 inch board as Small Bulky for 2026, yet its longest side exceeds the 37-inch Small Bulky limit in the same table. This checker follows the written limits, which would make that board Large Bulky. Confirm any borderline product with the Fee Preview report.
Sources
Every published rate and rule on this page was read from Amazon Seller Central on 18 October 2026, and where those pages are silent this page says so: Amazon Seller Central: Product size tiers, Amazon Seller Central: Dimensional weight, Amazon Seller Central: Shipping weight, Amazon Seller Central: Overmax handling fee. Seller Central is the source of truth and Amazon can change fees; check your own Fee Preview before you decide. This tool is independent and is not affiliated with or endorsed by Amazon. It runs in your browser and sends nothing anywhere.
FAQ
How does Amazon calculate dimensional weight?
Unit volume (length × width × height) divided by 139. For Small Bulky, Large Bulky, Overmax and Extra-Large items it assumes a minimum width and height of 2 inches.
Which weight sets my FBA fee?
Small standard-size units and Extra-Large 150+ lb units use unit weight. All other tiers use the greater of unit weight and dimensional weight.
What is the Overmax tier?
Extra-Large units up to 150 lb with a longest side over 96 inches or length plus girth over 130 inches. They pay an Overmax handling fee on top of the fulfillment fee.
Can I trust a tier from this page for a listing?
Treat it as a check. Amazon may verify weight and dimensions with samples and uses its own measurements to calculate fees.