About

TopMarginCalculator is a free set of profit calculators built for small business owners, side hustlers and online marketplace sellers. Every selling platform has its own fee structure, and most of them go out of their way to make the real cost of a sale hard to see. The goal of this site is simple: give you an accurate number, in seconds, without making you sign up for anything.

What you’ll find here

Five calculators, each one designed around how a specific platform actually charges sellers in 2026:

• Profit Margin Calculator — the universal sale-price / margin / markup / cost tool, with four calculation modes.
• Etsy Profit Calculator — listing, transaction, payment processing and Offsite Ads fees.
• Amazon FBA Profit Calculator — referral, FBA fulfillment, storage and Pro Plan amortisation.
• eBay Profit Calculator — final value fees, per-order charges, international fees and Top Rated Plus discount.
• Shopify Profit Calculator — payment processing by plan and the third-party gateway surcharge.

How we keep the fee data accurate

Every fee figure on every calculator is stored as a named constant in the project’s source code, with the year it was verified. When a platform updates a fee, we update the constant and republish — usually within a few weeks of an announcement. Every calculator page also carries a visible “current as of 2026” note with a link to the platform’s official fee policy so you can cross-check before pricing an important listing.

What we’re not

TopMarginCalculator is independent and is not affiliated with Etsy, eBay, Amazon, Shopify or any other platform. The calculators are for general guidance and are not financial, tax or legal advice — see the disclaimer for more.

Get in touch

Spotted a fee that’s changed, found a bug, or just have a request for a calculator we should add? Drop a note via the contact page.