Business math, made visible
Contribution margin calculator
Contribution margin calculator
Measure how much each sale contributes toward fixed costs.
Inputs stay in this browser. Results use your entries and the formula below.
This calculator shows the difference between selling price and variable cost per unit, plus that difference as a share of selling price. The SBA uses this contribution relationship in its break-even method. Enter the amounts for one consistently defined unit, such as an item, a pound, or a service hour. Fixed costs are not subtracted here. The result is the amount each sale can contribute toward those costs before the single-product break-even point is reached.
Worked example
| Source item | Published value |
|---|---|
| Selling price per pound | $1.00 |
| Variable cost per pound | $.50 |
| Amount toward fixed costs | $.50 per-pound-sold |
The NOAA-hosted example states that $.50 per pound sold applies toward fixed costs. Dividing $.50 by its $1.00 selling price gives a calculated contribution ratio of 50%. The ratio is derived from the cited example inputs. Source: NOAA repository: seafood retail break-even example, page 117.
How it works
Contribution per unit = selling price - variable cost per unit
Contribution ratio (%) = contribution per unit / selling price * 100
Formula basis: SBA: break-even and contribution formulas. Ratios are converted to percentages for display. Intermediate values retain full calculation precision; displayed amounts are rounded.
Separate variable and fixed costs
This tool uses variable cost for each unit. Fixed costs are handled separately in the break-even calculator. Putting a fixed cost allocation into the variable-cost field changes what the result measures and can count fixed costs again later. The SBA explains that mixed costs should be separated into their fixed and variable parts where possible. Keep that distinction consistent when moving between the two tools.
Choose between the amount and the ratio
The contribution amount is useful when reasoning about a number of identical units. The ratio is useful when expressing contribution relative to sales dollars. They describe the same relationship with different units. A comparison between products needs consistent cost definitions, and a total business calculation also needs the product mix. This page supplies the unit calculation without assuming which products will sell.
Use negative contribution as a signal in the model
A price below variable cost creates negative contribution. The tool displays that result instead of turning it into a positive amount. A price equal to variable cost produces zero contribution. In either case, additional units do not cover positive fixed costs under the simple break-even assumptions. A positive contribution still is not net profit because the fixed costs have yet to be covered.
Use the formula in a spreadsheet
Put selling price in A1 and variable cost per unit in B1. Use =A1-B1 for contribution per unit and =(A1-B1)/A1 for the ratio. Format the ratio as a percentage, and use the unit contribution as the denominator in the break-even units calculation.
Frequently asked questions
What is contribution margin per unit?
It is selling price per unit less variable cost per unit. This is the amount available from that sale toward fixed costs.
How do I calculate the contribution margin ratio?
Divide the per-unit contribution by selling price per unit. The tool displays the result as a percentage.
Is contribution margin net profit?
No. This calculation leaves fixed costs outside the subtraction. Net profit uses a different expense basis.
How does it connect to break-even?
The single-product break-even formula divides fixed costs by positive contribution per unit. The break-even calculator performs that additional step.
Can I use the contribution formula in Excel?
Yes. Subtract variable cost from selling price, then divide the difference by selling price for the ratio.
Can contribution margin be negative?
Yes. If variable cost exceeds the selling price, the sale creates a negative contribution on the entered cost basis.
Sources
- SBA: break-even and contribution formulas
- NOAA repository: seafood retail break-even example, page 117
Data as of 2026-10-05. Examples are historical teaching examples, not current prices or market benchmarks. Calculated results are derived from entered values.
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