Accounting Contribution Margin Formula
Learn how to calculate contribution margin, contribution margin ratio, contribution per unit, and variable cost per unit.
Contribution margin measures the sales revenue remaining after variable costs. It helps show how much a product, service, or sales mix contributes toward fixed costs and profit before those other expenses are deducted.
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Contribution Margin
Where:
Subtract total variable costs from sales revenue. The amount left is the contribution margin.
Variables Explained
| Variable | What It Means | Unit |
|---|---|---|
| salesRevenue - Sales revenue | Total revenue earned from the products or services during the period. | currency |
| variableCosts - Total variable costs | Costs that vary directly with sales or production volume during the same period. | currency |
| unitsSold - Units sold | Number of units sold during the same period. | number |
| contributionMargin - Contribution margin | Revenue remaining after total variable costs are deducted. | currency |
Step-by-Step Calculation
Record sales revenue
Use total sales revenue for a defined accounting period.
salesRevenue
Identify total variable costs
Include costs that vary with volume, such as direct materials, sales commissions, or per-order delivery costs when applicable.
variableCosts
Calculate contribution margin
This is the total amount available to cover fixed costs and then profit.
salesRevenue - variableCosts
Calculate contribution margin ratio
This shows the percentage of each revenue unit retained after variable costs.
(contributionMargin / salesRevenue) * 100
Calculate contribution per unit
This gives the average contribution made by each unit sold.
contributionMargin / unitsSold
Calculate variable cost per unit
This gives the average variable cost assigned to each unit sold.
variableCosts / unitsSold
Worked contribution margin calculation
Contribution margin
100000 - 60000
$40,000
Contribution margin ratio
(40000 / 100000) * 100
40.0%
Contribution per unit
40000 / 1000
$40.00 per unit
Variable cost per unit
60000 / 1000
$60.00 per unit
Final Result
The business has a contribution margin of $40,000, a 40.0% contribution margin ratio, and $40.00 contribution per unit.
Assumptions
- ✓Sales revenue, variable costs, and units sold cover the same accounting period.
- ✓Only costs that change directly with sales or production volume are included as variable costs.
- ✓Revenue is measured consistently with the related variable costs.
- ✓Fixed operating costs, interest, taxes, and other non-variable expenses are excluded.
Limitations
- !The calculation does not show net profit because fixed costs are not deducted.
- !A single average per-unit result can hide different margins across products, customers, or sales channels.
- !Cost classifications may differ between businesses and accounting methods.
- !Returns, discounts, inventory changes, and timing differences can affect reported results.
Common Mistakes to Avoid
Using fixed expenses such as rent or salaried administration costs as variable costs.
Comparing sales revenue from one period with costs or units from another period.
Confusing contribution margin with gross margin or net profit.
Dividing by units produced instead of units sold when the calculation is intended to use sales-period results.
Using a percentage such as 40 instead of 0.40 in a ratio calculation without multiplying correctly.
Related Formulas
Frequently Asked Questions
What is the formula for contribution margin?
Contribution margin equals sales revenue minus total variable costs.
How do you calculate contribution margin ratio?
Divide contribution margin by sales revenue, then multiply by 100.
How is contribution margin per unit calculated?
Divide total contribution margin by the number of units sold in the same period.
Is contribution margin the same as profit?
No. Contribution margin is calculated before fixed costs and other non-variable expenses are deducted.
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