Profit Margin Calculator for every reseller marketplace

Reseller profit is one of those numbers that feels obvious until you sit down to compute it. Sale price minus cost minus fees minus shipping — sounds easy. But every marketplace structures fees differently, payment processing is its own line item, shipping eats a chunk most sellers underestimate, and the same item can show wildly different margins depending on where you list it.

The calculator above runs the math the way the marketplaces actually charge it: a final value fee on the sale price (sometimes including shipping, like eBay does), a separate payment processing fee on the buyer's total, any per-listing fees that apply, and your real out-of-pocket sourcing cost. The Marketplace Comparison panel surfaces the side-by-side delta so you can see at a glance whether a $40 sweater clears more on Poshmark or eBay before you commit.

A few things sellers consistently get wrong:

• Fees often apply to shipping. eBay's final value fee is calculated on the total amount of the sale — item plusshipping and sales tax — and Mercari's 10% includes buyer-paid shipping. On a $40 item with $15 shipping, eBay's 13.6% comes out of the full $55 ($7.48, plus a $0.40 per-order fee), not $40. Depop has no selling fee, but its 3.3% + $0.45 processing is charged on item price, shipping and tax.
• Flat per-order fees bite hard on cheap items.Depop's $0.45 processing fee is nothing on a $100 sale — but it's 4.5% on a $10 sale. If you sell low-priced items, the flat fee structure matters more than the percentage.
• Promoted Listings aren't in base fee tables.If you opt into eBay Promoted Listings or paid promotion on another marketplace, or Etsy Offsite Ads apply to a sale, you're paying extra on top of base fees on the listings that sell through ads. Always check whether the sale was ad-attributed before assuming the fee number you calculated.
• Shipping isn't free even if it looks free."Free shipping" means the seller is paying. If you offer free shipping at checkout, that cost comes straight out of your margin and needs to be in the calculator's shipping field.
• Sourcing cost includes everything you spent.If you drove an hour to a thrift store, paid $5 for the item, and spent $3 in gas plus 30 minutes of your time — the real cost is closer to $15-20 once you value your time honestly. Most sellers track only the cash cost and end up working for less than minimum wage on low-margin items.

Once you have the math right, the bigger question becomes platform selection. Fee deltas of a few percentage points matter less than sell-through differences. A 13% fee on an item that sells in three days beats an 8% fee on an item that sits for six months. Use the calculator to compare margins, but pick your marketplace based on where your specific item actually moves.