Use the margin calculator in seconds
Gross profit is sale price minus cost. Margin divides that profit by sale price; markup divides it by cost. A zero sale price makes margin undefined, and a zero cost makes markup undefined, rather than 0%. Zero amounts are allowed, but blanks, negative values and out-of-range inputs produce errors. A sale below cost shows a loss. Enter both amounts in the same currency and on the same per-sale basis. The currency selector changes display labels only, not exchange rates. Percentages round to two decimal places; overhead, fees and taxes are excluded unless included in cost, so gross profit is not net income.