Two percentages with different denominators
Markup describes an increase over cost. Profit margin describes the share of sales left after the costs included in your model. Confusing them can produce a selling price that misses your target even before payment fees.
Work at the order level
Enter production cost per part and the quantity in one order. Then add the shipping cost you pay for that order and any fixed transaction fee. The percentage fee applies to the complete quoted order amount.
This calculator includes shipping in the quoted price. Do not charge it a second time using the same result unless you deliberately rebuild the model for a separate shipping line. Enter your actual provider’s fee schedule; the example percentage is not a verified marketplace fee.
Understand the rounding
The order result is divided by quantity, and the per-part price rounds upward to cents for USD/EUR or whole won for KRW. The displayed order total is that rounded unit price multiplied by quantity, so the actual modeled margin may be slightly above the target.
Changing the currency label does not convert any amounts. When switching currency, replace all prices, shipping and fee values with numbers in that currency. The calculator does not obtain exchange rates.
Know what the result leaves out
The model is before tax and excludes discounts, refunds, advertising acquisition cost and overhead you have not included in production cost. If those matter, include a defensible allowance in your cost inputs and check the result against your own records.
A mathematically valid price is not proof that customers will buy. Fee plus target margin must be less than 100%; otherwise the denominator cannot produce a usable positive price. Zero entered costs can produce a zero quote, which is not a business recommendation.