A 3% fee plus $0.30 is not a 3% cost. The fixed part takes a larger share of a small payment. If your store sells low-priced products, that difference can matter more than a rounded dashboard percentage suggests.
Payment schedules vary by country, card, payment method, currency and agreement. Inspect a current provider pricing page and your own statement. This guide uses a chosen 3% plus $0.30 example. It is not a universal rate or a recommendation of one processor.
Calculate the effective fee
The fee is the percentage multiplied by the payment amount, plus the fixed charge. Divide that total by the payment amount to get the effective rate.
Swipe or scroll the table horizontally to see every column.
| Payment amount | Percentage part | Fixed part | Total fee | Effective rate |
|---|---|---|---|---|
| $10 | $0.30 | $0.30 | $0.60 | 6.00% |
| $20 | $0.60 | $0.30 | $0.90 | 4.50% |
| $50 | $1.50 | $0.30 | $1.80 | 3.60% |
| $100 | $3.00 | $0.30 | $3.30 | 3.30% |
At $20, calling the fee 3% misses $0.30. Across 1,000 such payments, that omitted fixed charge is $300. This is arithmetic under the stated schedule, not a measured industry loss.
Check the amount the percentage applies to
Does the provider charge on product revenue alone, or on the full payment including delivery and tax? Are there additional cross-border, currency-conversion or platform fees? Read the actual schedule and compare it with a completed transaction.
A product-margin report may exclude costs that the processor charges on a wider payment base. Enter actual total fees in the order profit calculator. That is safer than assuming the advertised percentage captures every charge. Keep the product revenue, shipping receipts and matched refunds separate.
For zero-value payments, an effective rate has no useful denominator. For very small payments, minimum fees or method-specific rules may replace this simple formula. Do not extend the example beyond the fee schedule it assumes.
A larger basket is not automatically better
Combining two purchases can reduce the number of fixed transaction charges. But a bundle discount, a heavier parcel or an additional ad cost may cost more than the fee saved.
Two $20 payments at the example rate cost $1.80 in total. One $40 payment costs $1.50, saving $0.30 in payment fees. If the bundle requires a $2 discount, fee savings alone do not cover that discount. Product cost is unchanged in this comparison; delivery and other costs still need checking.
Use the bundle pricing calculator for the whole offer, and read the margin versus markup guide if the percentages in your reports use different denominators. A fee percentage and a product markup are not interchangeable.
Refunds need a second check
A refunded sale does not necessarily reverse every original payment fee. Provider and payment-method rules differ. Match a refund to the original transaction and read the fee entries rather than assuming the full charge was returned. Our return-cost scenarios let you choose how much of the original fee is recovered.
Keep the original fee, any recovered fee and extra return costs separate. Otherwise an order can disappear from net sales while its processing cost remains hidden in another report.
A quick statement review
Choose several real transactions with different basket sizes. Record the charged amount, total fees, currency and method. Recalculate each effective rate. Explain differences using the schedule before calling them an error.
Then repeat the contribution calculation for the products you actually sell. The useful question is what remains after the costs, not which headline percentage is smallest. If you request a manual review, remove payment credentials and customer details; a few anonymized totals and the relevant fee terms are enough to start.