• The definition
  • The formulas

Contribution margin is the selling price of a product or service minus its variable costs: the costs that rise with each unit you sell, such as materials, contractor fees or payment processing. What's left is what each sale contributes toward your fixed costs, like rent and salaries, and, once those are covered, toward profit. As a percentage of the price, it's the contribution margin ratio.

The definition

OpenStax's Principles of Accounting, Volume 2: Managerial Accounting (section 3.1, opened October 29, 2026) defines it:

"Contribution margin is the amount by which a product's selling price exceeds its total variable cost per unit. This difference between the sales price and the per unit variable cost is called the contribution margin because it is the per unit contribution toward covering the fixed costs."

It defines the ratio as "the percentage of a unit's selling price that exceeds total unit variable costs."

It defines the two kinds of cost this way:

  • "Fixed costs are those costs that will not change within a given range of production."
  • "Variable costs are those costs that vary per unit of production."

The formulas

  • Contribution margin per unit = selling price per unit − variable cost per unit.
  • Contribution margin ratio = contribution margin per unit ÷ selling price per unit.
  • Total contribution margin = contribution margin per unit × units sold.
  • Break-even units = fixed costs ÷ contribution margin per unit.
  • Break-even sales = fixed costs ÷ contribution margin ratio.

OpenStax (section 3.2) describes the break-even point as "the dollar amount (total sales dollars) or production level (total units produced) at which the company has recovered all variable and fixed costs."

Worked example: a service package

The figures here are a sample. A studio sells a service package for $200. Each package costs $70 in contractor fees and $10 in payment processing, so its variable cost is $70 + $10 = $80. The studio's fixed costs are $30,000 a month.

  1. Contribution margin per package: $200 − $80 = $120.
  2. Contribution margin ratio: $120 ÷ $200 = 0.60, or 60%. Sixty cents of each sales dollar goes toward fixed costs and profit.
  3. Break-even packages: $30,000 ÷ $120 = 250 packages a month.
  4. Break-even sales: $30,000 ÷ 0.60 = $50,000 a month. Check: 250 × $200 = $50,000.
  5. Profit at 300 packages:
    • total contribution margin = 300 × $120 = $36,000;
    • profit = $36,000 − $30,000 = $6,000;
    • check: sales 300 × $200 = $60,000, less variable costs 300 × $80 = $24,000, less fixed costs $30,000, leaves $6,000.

You can run the same numbers with the break-even calculator. To see margin as a share of price, try the profit margin calculator.

How to use it

  • Pricing and discounts. A discount comes straight off the contribution margin. In the example, a $40 discount cuts the margin from $120 to $80 per package, so break-even rises to $30,000 ÷ $80 = 375 packages.
  • Comparing offers. Compare products or services by their contribution margin, not just their price. A cheaper offer with low variable costs can contribute more per sale than a pricier one.
  • Planning. Total contribution margin minus fixed costs is your profit, so you can see what volume you need for a profit target.

Contribution margin vs. gross profit

Contribution margin subtracts only variable costs. Gross profit subtracts the cost of goods sold as your books record it, which can include costs that don't vary with each sale. The two can differ, so label which one you're using. Contribution margin is mainly for internal decisions like pricing and break-even planning.

Where Billed fits

Billed's expense and receipt tracking page describes giving each expense a category and an expense report that "can group your expenses by category." Categories that separate variable costs, such as contractor fees, from fixed costs, such as rent, give you the inputs for this calculation. Billed's expense and receipt tracking page doesn't calculate contribution margin, so use the calculators linked above or your own spreadsheet.

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Frequently Asked Questions

How do you calculate contribution margin?

Subtract the variable cost per unit from the selling price per unit. A $200 package with $80 of variable costs has a contribution margin of $120. Divide by the price ($120 ÷ $200) for the contribution margin ratio, here 60%.

What is the contribution margin ratio?

It's the contribution margin as a percentage of the selling price. OpenStax describes it as "the percentage of a unit's selling price that exceeds total unit variable costs."

How does contribution margin relate to the break-even point?

Divide your fixed costs by the contribution margin per unit to get the number of units you need to sell to break even. Divide fixed costs by the contribution margin ratio to get break-even sales in dollars.

What is the difference between contribution margin and gross profit?

Contribution margin subtracts only the costs that vary with each sale. Gross profit subtracts the cost of goods sold as your books record it, which can include costs that don't change with each sale. Contribution margin is mainly used for pricing and break-even decisions.

Can contribution margin be negative?

Yes, if the variable cost per unit is higher than the selling price. Then each sale adds to your losses instead of covering fixed costs, so you'd need to raise the price or lower the variable costs.

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