Mercari's selling fee is 10% of the item price plus any shipping the buyer paid. There is no listing fee, and for listings created or edited since January 6, 2025 there is no separate payment processing fee. Buyers pay a 3.6% Buyer Protection fee at checkout, which does not come out of your payout.
Your shipping choice changes where the 10% lands. If the buyer pays shipping, it joins the fee base, so you pay 10% on the label money too. If you offer free shipping, the label comes out of your earnings instead and the fee is 10% of the item price alone.
Getting paid by direct deposit is free. Instant Pay to a debit card costs $3 per cash-out, not per sale, so the toggle treats this sale as one cash-out. Cash out several sales together and the $3 is shared among them.
Profit is the payout minus the item cost, your label, and packaging. ROI compares that profit with the item cost, the fastest way to judge a sourcing buy.
Selling fee = 10% x (item + buyer-paid shipping). Payout = item + buyer-paid shipping - selling fee [- $3 Instant Pay]