Methodology

There's no account, no database, and nothing you type is sent to a server. Every number on this site is computed by JavaScript running on your own device, from the rate tables and formulas described below. Nothing is saved once you close the tab, unless you save a share link yourself.

Internally, every amount is a whole number of cents (never a fraction of a cent), and every rate is a whole number of basis points (1% = 100 basis points). Every fee is rounded exactly once, using standard round-half-up rounding, from its own unrounded base — no fee is ever calculated from another fee's already-rounded output, and totals are the sum of already-rounded fees rather than a separately-rounded total. This avoids the small but real rounding drift that comes from mixing floating-point percentages.

A marketplace fee's base — the amount a rate is applied to — is one of: the sale price alone; the sale price plus any shipping the buyer pays at checkout; or that same amount plus sales tax. Which base a given fee uses is a documented, explicit choice for that fee, never a guess made at calculation time. Grailed is the clearest example of why this matters: its commission and its payment processing fee use different bases (commission depends on whether you use a Grailed shipping label; processing never does), and the two are calculated completely independently, even when the numbers happen to coincide for a particular order.

Some fee schedules charge a different rate depending on how much you sold something for. There are two different ways that can work, and mixing them up produces wrong numbers:

• Marginal tiers (like Whatnot's high-value categories) work like an income tax bracket: part of the sale is charged at one rate, the rest at another. The result changes smoothly as price goes up.
• Whole-amount tiers (Poshmark's $15 threshold, Grailed's $120 threshold) charge the ENTIRE sale at whichever single rate the price falls into. Crossing the threshold can make the fee jump by more than the extra cent of price justifies.

Because whole-amount tiers can jump by more than a price increase justifies, there are real, narrow price ranges just above a threshold where you'd net less than pricing just below it — for example, Poshmark at exactly $15.00 nets less than $14.99, and Grailed at exactly $120.00 nets less than $119.99. Each platform's calculator flags this automatically when your price falls in that range, and the Target Price calculator's search accounts for it directly: it doesn't just scan upward from zero and stop at the first price that looks close, because that naive approach can land on a higher price than necessary. Instead, it identifies every point where a fee schedule's behavior can change, breaks the price range into segments at those points, and searches each segment independently for the true minimum.

When the price itself is what we're solving for, we don't know it yet — so we can't also hold sales tax fixed while trying different candidate prices, because on platforms where tax feeds into a fee's base (Whatnot, Depop, Grailed), a fixed tax amount would distort the comparison as the price changes. Rather than approximate that, the Target Price calculator and each platform's "pricing trap" detection both assume $0 sales tax. If your state or the buyer's charges tax, your actual required price may differ slightly.

Every fee in every calculator carries one of three confidence levels:

• Official — the platform's own published terms state this rate, this base, or this threshold directly.
• Derived — no single official sentence states it in this exact form, but it follows directly from combining multiple facts the platform has published (for example, one page states a reduced rate for a category, another describes a promotional threshold that applies to that category, and we combine the two).
• Unverified (shown in the calculator as an "Unverified rate" badge) — we could not confirm this from an official source at all. It's included because leaving it out entirely would be less useful than an honestly-flagged estimate, but you should verify it yourself before relying on it for a large sale.

We'd rather flag an estimate as unverified than quietly guess at a number that looks plausible.

Each platform page shows exactly when its rates were last checked against an official source:

• Whatnot: verified 2026-09-16
• Depop: verified 2026-09-16
• Grailed: verified 2026-09-16
• Mercari: verified 2026-09-16
• Poshmark: verified 2026-09-16

Marketplace fees change. If something here looks out of date, the "View official fee source" link on each platform page goes straight to that platform's current terms.