Two percentages, two different denominators

Markup = (price − cost) / cost. Margin = (price − cost) / price. They describe the same dollars relative to different starting points.

A $30 cost with a 40% markup produces a $42 price. The $12 contribution is only 28.57% of that selling price. A 40% margin on a $30 cost instead requires a $50 price, leaving $20.

Calculate the price from a target margin

Without percentage fees, required price = cost / (1 − target margin). Express 40% as 0.40. The calculator rounds its suggested order price upward to the nearest cent rather than rounding down below the target.

A 100% margin on a nonzero cost has no finite price. When there are percentage fees, the sum of target margin and percentage fees must stay below 100%. Invalid combinations pause the result rather than producing a misleading price.

Do not forget payment fees

When a platform charges a percentage of the total selling price, adding that percentage to the cost is not enough. Required price = (production cost + fixed payment fee) / (1 − target margin − fee rate).

For $30 production cost, a $0.30 fixed fee, a 3% percentage fee, and a 40% target margin, the required price is $30.30 / 0.57, or $53.16 rounded up. The 3% here is an example, not a quoted rate from a payment provider.

Margin is not take-home pay

SpoolMargin calculates contribution after the costs and fees you enter. This is not accounting net profit. Unmodeled overhead and taxes can still reduce the result. A $0 selling price has undefined margin, which the calculator labels explicitly.

Check a discount at the actual selling price

Use the same $30 production cost, 3% fee and $0.30 fixed fee. If a customer offers $45, fees are $1.65, cost including fees is $31.65, and contribution is $13.35. Margin is $13.35 / $45 = 29.67%. A 10% discount from the suggested price does not reduce margin by exactly ten percentage points.

The fee-aware break-even price is ($30 + $0.30) / (1 - 0.03) = $31.2371, or at least $31.24 at cent precision. That covers only the entered costs. It does not compensate for omitted taxes, overhead or future uncertainty.

Use consistent definitions when comparing jobs

Compare contribution dollars as well as margin. A large order at a lower percentage can leave more contribution than a small order at a higher percentage, while still consuming more printer capacity and labor. The calculator does not schedule jobs or optimize revenue per machine hour.

Use the whole order price for a fixed transaction fee. If a platform collects the fee on shipping or tax as well, reconcile that fee base separately. Do not present the tool margin as audited profit or treat an unentered cost as zero in your records.