Rates checked at the source
Marketplace fees change often, and articles quoting them go stale fast. In just the past few months, Depop raised its boost rate, Whatnot moved to volume tiers, and Vinted renamed its buyer fee. Every calculator here uses rates read from the marketplace's own fee page, and each one shows the date it was last checked with a link so you can confirm it yourself.
Where a marketplace's own pages disagree or leave something unclear, the calculator page says so rather than quietly picking one. Facebook Marketplace is the main example at the moment. If your payout ever shows something different from a result here, trust the payout.
Which one do you need?
Deciding where to list something? Start with the reseller profit calculator, which compares every marketplace at once. At the thrift store, deciding whether to buy? The max buy price calculator works backwards from the sale to the most you should pay. If you already know where you are selling, the fee calculator for that marketplace has its specific options, such as eBay categories and Store pricing, and a full explanation of how its fees work.
Shipping can take more out of a sale than fees do, especially on anything bulky. The shipping estimator shows when a box is big enough to be charged by dimensional weight, and what that is likely to cost you. All of them recalculate as you type, and each one starts with a sample sale so you can see how it works before entering your own numbers.
Common questions
Are these calculators free?
Yes, and you do not need an account to use them.
How accurate are the results?
They use each marketplace's published rates, so they should be close, but treat them as estimates. Your real fees can vary with your account standing, your location and promotions. Your payout statement is the final word.
Which marketplaces are covered?
eBay, Poshmark, Mercari, Depop, Vinted, Facebook Marketplace, Etsy and Whatnot.