Amazon's fee staircase, on one page

1What sets the fee

• Tier. Sides sorted longest first. Small standard: up to 15 × 12 × 0.75 in and 16 oz. Large standard: up to 18 × 14 × 8 in and 20 lb.
• Weight band. Small standard climbs in 2-oz steps to 16 oz; large standard in 4-oz steps to 3 lb, then $0.08 for every 4 oz.
• Price band. Under $10, $10 to $50, over $50.
• Season. October 15 to January 14, the holiday card: $0.20 to $0.42 a unit more in the $10 to $50 column.
• Surcharge. 3.5% on every fulfilment fee since April 17, 2026.

2Read a listing

Five numbers: the Buy Box price, the item weight, the package (else product) dimensions, the top-level category and the sales rank.

lb × 16 = oz · cm ÷ 2.54 = in · g ÷ 28.35 = oz

The page's weight and product dimensions are floors: a finding built on them understates the fee. For your own SKUs, Fee Preview has Amazon's measurements.

3Find the step

1. Sort the sides, longest first.
2. Billable weight: over a cubic foot (1,728 cu in), the greater of the unit's weight and L × W × H ÷ 139 lb; under it, the unit's weight.
3. Tier, from the sides and the billable weight.
4. Column, from the price.
5. Row: the first whose edge the billable weight does not exceed. The fee is that cell, plus the surcharge.

4The four edges

• Weight band: within 2 oz past the edge below.
• Price band: at or above $10 or $50, where one cent under pays the cheaper column.
• Tier: exactly one side over small standard, by 35% or less, and 16 oz or less.
• Box: dimensional weight at least 1.3 × the real weight.

Each counts only at 8 cents a unit or more (Hubricon's thresholds, not Amazon's). Edges overlap: never add them; the largest single edge is the finding.

5The counterfactual

gap per unit = fee now − fee at the edge below, on both cards

net a unit at one cent under = fee jump − (P − (E − $0.01)) × (1 − r)

break-even price = (E − $0.01) + fee jump ÷ (1 − r)

months to pay back = one-time cost ÷ (gap per unit × units a month)

P is the price, E the edge ($10 or $50), r the referral rate. The price move costs nothing to make, so it usually goes first.

6Volume, as a range

units a month ≈ scale × 10^(5.925 − 0.875 × log10(rank))

For a rank of 1,000 or worse in a top-level category. Never a point: half to one and a half times in plain arithmetic. Your own units, from Business Reports, beat the curve.

Simulated (lesson 6): volume × e^σz with σ = ln 2 ÷ 1.645, cost × (0.9 + 0.2 × a random number). Plan on P10; say the range, rounded down.

7The 271-day cliff

The aged surcharge goes from $1.50 to $5.45 a cubic foot a month at day 271, from Amazon's snapshot on the 15th.

days of cover = units on hand ÷ units sold a day

Above about 270 days of cover, some units cross before they sell. Before the 15th: sell the oldest through, remove them, or liquidate. Your ages: Reports, Fulfillment, Manage Inventory Health.

8Every SKU, in order

1. Sort by Rank: the low end of what each SKU's largest edge is worth a year.
2. Price edges first; they cost nothing. Then packaging, each against its quote.
3. Stop where a year at the low end is less than the change costs.

"Amazon's fee minus this sheet's" above zero: weigh and measure a packed unit, and if Amazon is wrong, open a case. Run it every quarter, and the week Amazon publishes a new card.