Methodology

How every fee figure on this site is sourced, checked, and turned into a calculation — including the things we deliberately do not model.

A fee calculator is only worth as much as the numbers behind it. This page documents exactly where ours come from so you can verify any figure yourself, and so you know the edges of what the tools can tell you. All14 fee schedules on the site are currently drawn from12 official sources; the most recent review wasJuly 2, 2026.

Where the numbers come from

We use primary sources only: the marketplace’s own published pricing page, rate card, or seller help-centre fee schedule. We do not copy figures from blog posts, competitor calculators, or aggregator sites, because those go stale silently and reproduce each other’s mistakes. Where a marketplace publishes a rate only inside a signed-in seller account, we say so rather than guess.

Every dataset below is a JSON file in this site’s source, validated against a schema at build time — a malformed or missing rate fails the build rather than shipping a silent zero. The table is generated from those same files, so what you see here is what the calculators actually use.

“Last reviewed” means a person opened that source and compared it line by line against our stored figures on that date — not that the marketplace changed its fees on that date.

How often we re-check

Marketplaces rarely announce fee changes loudly, and when they do it is often weeks before the change takes effect. Rather than re-verify everything at once and let it all age together, we run a rotating spot check: on a regular cadence we take the next marketplace in the rotation, open its official source, and compare the headline rates — referral or final value fee percentages, per-order fees, minimums, and plan pricing — against what we store.

One of three things happens:

• Rates match — we bump the review date and record that nothing changed.
• Rates differ — we correct the data file, update the review date, and the change flows to every calculator, fee page and comparison that uses it.
• Source unreachable — if a page is gated, moved, or down, we record that we could not verify and leave the figures untouched. We never “refresh” a date we did not actually check, and we never adjust a rate on the basis of a secondary source.

Fee schedules that move together are stored per region rather than converted, so a UK rate change never silently alters a US calculation.

How a published fee schedule becomes a calculation

Most of the modelling difficulty is in price bands. Marketplaces use two different mechanics and the difference is worth real money.

Whole-price bands

The item’s price decides which single rate applies to the entire sale. Amazon’s US clothing category works this way: 5% at $15 or less, 10% from $15.01 to $20.00, and 17% above $20.00. Because the rate applies to the whole price, the band edges create a genuine cliff:

Two cents more on the sticker leaves you $1.38 worse off. Our calculators reproduce this exactly, using each marketplace’s documented inclusive edges — which is the main reason a rounded “about 15%” estimate is not good enough near a threshold.

Per-portion (marginal) rates

The other mechanic charges one rate on the first slice of the price and a different rate on the rest — for example 15% on the portion up to $100 and 8% on the portion above it. This needs cumulative maths and behaves nothing like a whole-price band. Where a category works this way and we have not modelled it, we say so in the limitations below rather than quietly applying the headline rate as if it were flat.

Minimums and per-order fees

Percentage rates are not the whole story on low-priced items. Amazon applies a $0.30 minimum referral fee per item, so a $1.50 health & beauty item does not pay 8% ($0.12) — it pays $0.30, an effective 20%. eBay adds a fixed per-order fee that steps with the order total, and Etsy charges a listing fee plus a fixed component on payment processing. Our calculators apply these floors and fixed amounts, which is why our effective-rate figures on cheap items look higher than a marketplace’s headline percentage.

Where fees are themselves taxed — UK and EU sellers pay VAT on marketplace fees — we model that on top of the fee, and treat it as reclaimable for VAT-registered sellers rather than folding it into net profit.

What we deliberately do not model

A calculator that pretends to capture every possible charge would be less useful than one with clear edges. These are ours:

Across all marketplaces we also exclude things that depend on your specific account rather than the published schedule: negotiated or promotional rates, advertising spend, refunds and chargebacks, returns-processing charges, inbound shipping to a fulfilment centre, and income tax. Sales tax and VAT collected from buyers is generally remitted by the marketplace and is not treated as your revenue.

Corrections

If a figure here disagrees with what your seller account charges you, the seller account is right and we want to know. Email[email protected] with the marketplace, region, and ideally a link to the official page showing the current rate. We check reports against the primary source, correct the data file, and the fix appears on every page that uses it.

These calculators are planning tools built on published rates. They are estimates, not quotes — see our Terms & Disclaimer, and confirm against the marketplace’s official schedule before committing to inventory or pricing. More about who runs the site is on theAbout page.

Most recent data review: July 2, 2026