Before building Margin Calculator, we checked a widely used online margin calculator directly.
Margin vs markup calculator, done correctly
It gets the fundamental distinction right and shows both: margin (profit ÷ revenue) and markup (profit ÷ cost) side by side for the same numbers — exactly the pairing that prevents pricing mistakes from mixing the two up. We kept that same dual display.
Profit margin after marketplace fee, not before
What it doesn't handle: cost is treated as one flat number, with nowhere to account for a payment processor or marketplace taking a percentage off the sale — Stripe, Etsy, Amazon, and similar platforms all do this. If you sell through one of those, your real margin is lower than what a plain cost-vs-price calculation shows.
Net profit margin calculator, with the fee visible
Add a selling fee percentage and this tool shows the fee amount separately, then computes margin and markup on what you actually keep — not the gross sale price.