Quick answer
Contribution per unit = selling price − variable cost, and the ratio is contribution ÷ price. A $50 item with $30 of variable cost contributes $20 per unit, a 40% contribution margin.
Enter the selling price and the variable cost per unit. The calculator returns the contribution and the margin ratio.
Related tools: Break-Even Calculator: Units and revenue needed to cover fixed and variable costs. ROI Calculator: Return on investment, with optional annualized return. Markup Calculator: Selling price from cost and markup percentage.
How to use the Contribution Margin Calculator
- Enter selling price per unit ($) (above 0).
- Enter variable cost per unit ($) (0 or more).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Selling price per unit | A number, in $ | > 0 |
| Variable cost per unit | A number, in $ | ≥ 0 |
Formula and method
Formula
contribution = price − variable cost; ratio = contribution ÷ price
IEEE-754 double precision; shown to the decimals indicated.
Fixed costs are excluded.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Selling price per unit = 50; Variable cost per unit = 30.
| Result | Value |
|---|---|
| Contribution per unit | $20.00 |
| Contribution margin ratio | 40% |
Example 2
Inputs: Selling price per unit = 12.5; Variable cost per unit = 4.
| Result | Value |
|---|---|
| Contribution per unit | $8.50 |
| Contribution margin ratio | 68% |
The first line is the headline result (contribution per unit). Below it the contribution Margin Calculator lists contribution margin ratio, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
What it is used for
Contribution covers fixed costs first and then becomes profit. At 40%, every $1,000 of sales contributes $400. Divide fixed costs by the ratio to find the break-even revenue: $8,000 of fixed costs needs $20,000 of sales.
Negative contribution
If variable cost exceeds the price, each sale loses money and more sales make the loss bigger. The calculator shows the negative figure. Contribution margin differs from gross margin, which also subtracts fixed production costs.
How the result changes with selling price per unit
Holding every other input at the first worked example, this table changes only selling price per unit. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Selling price per unit | Contribution per unit | Contribution margin ratio |
|---|---|---|
| 25 | -$5.00 | -20% |
| 50 | $20.00 | 40% |
| 100 | $70.00 | 70% |
| 200 | $170.00 | 85% |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Selling price per unit: entering "0" shows "Selling price per unit must be greater than 0." beside that field and no result.
- Variable cost per unit: entering "-1" shows "Variable cost per unit must be at least 0." beside that field and no result.
Choosing between the Contribution Margin Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Break-Even Calculator](/business/break-even/) | fixed costs, price per unit and variable cost per unit | Break-even units |
| [ROI Calculator](/business/roi-calculator/) | amount invested and final value | ROI |
| [Markup Calculator](/business/markup-calculator/) | cost and markup | Selling price |
| [Margin Calculator](/business/margin-calculator/) | cost and revenue | Gross margin |
| [EBITDA Margin Calculator](/business/ebitda-margin-calculator/) | revenue and eBITDA | EBITDA Margin |
Background: business metrics
Business ratios depend on exactly which costs and revenues you include, so read each page's definition. Two common checks: break-even units = fixed costs ÷ (price − variable cost per unit), so $50,000 of fixed costs with a $10 price and $5 variable cost breaks even at 10,000 units; and net profit margin = net profit ÷ revenue, so $20,000 profit on $100,000 revenue is 20%.
Return on investment ignores time: 20% over five years is far less impressive than 20% in one, so compare returns over the same period.
Assumptions and limitations
- Variable cost can exceed price (negative contribution)
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for selling price per unit and variable cost per unit to confirm this.
Frequently asked questions
What counts as a variable cost?
Costs that change with each unit sold, such as materials and per-unit shipping.
Is higher always better?
A higher ratio means more of each sale goes to fixed costs and profit.
How is it different from profit?
Profit also subtracts fixed costs.
What does the Contribution Margin Calculator calculate?
Per-unit contribution and contribution margin ratio. It returns Contribution per unit and Contribution margin ratio.
What formula does the Contribution Margin Calculator use?
contribution = price − variable cost; ratio = contribution ÷ price. Fixed costs are excluded.
What do I need to enter in the contribution Margin Calculator?
You enter Selling price per unit ($) and Variable cost per unit ($).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Variable cost can exceed price (negative contribution).
What is an example of a contribution Margin result?
With selling price per unit 50 and variable cost per unit 30, the contribution per unit is $20.00.
Related calculators
- Break-Even Calculator — Units and revenue needed to cover fixed and variable costs.
- ROI Calculator — Return on investment, with optional annualized return.
- Markup Calculator — Selling price from cost and markup percentage.
- Margin Calculator — Profit, gross margin and markup from cost and revenue.
- EBITDA Margin Calculator — EBITDA as a share of revenue.
- Operating Margin Calculator — Operating income as a share of revenue.
- Net Profit Margin Calculator — Net profit as a share of revenue.
- Revenue Calculator — Revenue from price and units sold.
Sources
- OpenStax, Principles of Accounting, Volume 2: Managerial Accounting (Rice University)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.