How the calculators work
One fee engine, ten platforms, every rule written down. This page is for anyone who wants to check our numbers.
Sources
Every fee comes from the platform's own published fee schedule or seller help centre. We do not use third-party summaries as the source of record. The schedules were last fully re-verified on 2026-10-16.
- Etsy: https://help.etsy.com/hc/en-us/articles/115014483627
- eBay: https://www.ebay.com/help/selling/fees-credits-invoices/selling-fees?id=4822
- Mercari: https://www.mercari.com/us/help_center/
- Poshmark: https://support.poshmark.com/s/article/1200000038447-Fees
- Depop: https://help.depop.com/hc/en-gb/articles/360001764628
- Vinted: https://www.vinted.co.uk/help/397-selling-fees
- Whatnot: https://help.whatnot.com/hc/en-us/articles/4408660117133
- StockX: https://stockx.com/help
- TikTok Shop: https://seller-us.tiktok.com/university/
- Amazon: https://sell.amazon.com/pricing
What each fee is calculated on
The most common error in fee calculators is applying a percentage to the wrong base. Our engine encodes the base for every line:
- Item only: Poshmark commission, Whatnot commission, StockX transaction and processing fees, TikTok affiliate commission.
- Item + buyer-paid shipping: Etsy transaction fee, Mercari selling fee, Depop processing, TikTok Shop referral fee, Amazon referral fee, eBay Promoted Listings.
- Item + shipping + sales tax: eBay final value fee, Etsy payment processing, Whatnot payment processing.
Sales tax is an optional "more options" input on platforms where it affects fees, because sellers rarely know it in advance. Leaving it at zero slightly understates eBay, Etsy and Whatnot fees in US states with sales tax.
Definitions
- Buyer pays you: item price plus shipping you charged. Buyer-side platform fees (Vinted, Depop US, Mercari) are shown as a note, not included, because they never reach you.
- Total fees: sum of every seller-side fee line.
- Payout: buyer pays you minus total fees. This is what the platform deposits.
- Profit: payout minus your item cost minus your shipping cost. Income tax is not included.
- Margin: profit divided by item price.
- Fees as % of sale: total fees divided by buyer-pays-you.
Rounding
Each fee line is calculated in full precision and rounded to the cent for display. Totals are summed from unrounded lines, so a total can differ by one cent from the sum of displayed lines. Platforms round each fee line themselves, so a real statement may also differ by a cent or two.
What is deliberately left out
- Monthly subscriptions (Amazon Professional $39.99, eBay Stores) because they are not per-sale costs. Their effect on per-sale rates is noted where relevant.
- Amazon FBA storage, inbound placement, low-inventory and returns processing fees, which depend on your whole catalogue.
- Currency conversion fees, refunds, chargebacks and dispute fees.
- Your income tax and sales tax obligations.
Reporting an error
If a platform has changed a fee and we have not caught it, or you believe a calculation is wrong, contact us with the platform, the input values and a link to the platform's own documentation. Corrections are logged on the fee change log.