The formula
- Processing fee = payment × percentage rate + fixed fee
- Net amount = payment − fee
- Effective rate = fee ÷ payment
- Price that covers the fee = (amount you want + fixed fee) ÷ (1 − percentage rate)
Standard US online rates (flat-rate processors)
| Processor | Standard online card rate |
|---|---|
| Stripe | 2.9% + 30¢ (+1.5% international, +1% conversion) |
| WooPayments | 2.9% + 30¢ (+1.5% international, +1% conversion) |
| Square — Free plan | 3.3% + 30¢ |
| Square — Plus / Premium plans | 2.9% + 30¢ |
| PayPal — standard card payments | 2.99% + 49¢ |
| PayPal — PayPal Checkout button | 3.49% + 49¢ |
Rates from each provider’s US pricing page, checked on the date at the top of this page. Pick a processor in the calculator to add international and conversion surcharges, or keep “Custom rate” for your own contract.
Flat-rate vs interchange-plus
Flat-rate pricing (the table above) is simple and predictable — good for small and growing stores. Interchange-plus passes through the card network’s actual cost (which varies by card type) plus a fixed markup; it’s usually cheaper above roughly $50–100k per month in card volume, but harder to predict. If you’re on interchange-plus, enter your average effective rate as the custom percentage.
What the monthly total tells you
Enter the number of payments per month to see fees per month and per year. A 0.3% difference in rate on $30,000 of monthly sales is $1,080 a year — worth a phone call to your processor, but rarely worth a migration on its own.
For provider-specific details see the PayPal and Stripe fee calculators.