Monthly Contribution Margin Formula
Learn how monthly contribution margin, contribution margin ratio, operating income, and break-even sales are calculated from revenue and costs.
Monthly contribution margin estimates the revenue left after costs that change with sales have been paid. It helps show how much is available to cover fixed monthly costs and generate operating income from the items included in the calculation.
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Monthly Contribution Margin
Where:
Subtract monthly variable costs from monthly sales revenue. The amount left is available to pay fixed costs and, after those costs are covered, contribute to operating income.
Variables Explained
| Variable | What It Means | Unit |
|---|---|---|
| monthlyRevenue - Monthly sales revenue | Total sales revenue for one month before deducting costs. | currency |
| monthlyVariableCosts - Monthly variable costs | Costs that generally change with sales volume or revenue, such as materials, commissions, shipping, and transaction fees. | currency |
| monthlyFixedCosts - Monthly fixed costs | Costs that generally remain stable over the relevant sales range, such as rent, core salaries, and subscriptions. | currency |
| contributionMargin - Monthly contribution margin | Revenue remaining after monthly variable costs are deducted. | currency |
| contributionMarginRatio - Contribution margin ratio | The percentage of revenue remaining after variable costs. | percent |
Step-by-Step Calculation
Calculate monthly contribution margin
Remove the costs that vary with sales from monthly revenue.
contributionMargin = monthlyRevenue - monthlyVariableCosts
Calculate the contribution margin ratio
Divide contribution margin by revenue and convert the result to a percentage.
contributionMarginRatio = contributionMargin / monthlyRevenue * 100
Calculate estimated operating income
Subtract the entered monthly fixed costs from contribution margin.
operatingIncome = contributionMargin - monthlyFixedCosts
Calculate break-even monthly sales
Divide fixed costs by the contribution margin ratio expressed as a decimal. This estimates sales needed for contribution margin to equal fixed costs.
breakEvenSales = monthlyFixedCosts / (contributionMarginRatio / 100)
Monthly contribution margin calculation example
Contribution margin
$50,000 − $30,000
$20,000
Contribution margin ratio
$20,000 ÷ $50,000 × 100
40%
Estimated operating income
$20,000 − $15,000
$5,000
Break-even monthly sales
$15,000 ÷ 0.40
$37,500
Final Result
Monthly contribution margin is $20,000, the contribution margin ratio is 40%, estimated operating income is $5,000, and estimated break-even monthly sales are $37,500.
Assumptions
- ✓Revenue, variable costs, and fixed costs all relate to the same monthly period.
- ✓Variable costs are assumed to move proportionately with sales revenue.
- ✓Fixed costs are assumed to remain unchanged within the relevant range of monthly sales.
- ✓The current contribution margin ratio is assumed to continue at the break-even sales level.
- ✓Only the costs entered are included; the calculation excludes unentered items.
Limitations
- !Actual variable cost percentages can change because of discounts, supplier pricing, returns, product mix, or capacity constraints.
- !Some costs are mixed, meaning they have both fixed and variable elements and may need to be split before using the calculator.
- !Estimated operating income excludes items not entered, which may include interest, taxes, depreciation, owner drawings, and unusual one-off costs.
- !Break-even sales are not meaningful when revenue does not exceed variable costs and the contribution margin ratio is zero or negative.
Common Mistakes to Avoid
Entering annual costs with monthly revenue, or the reverse.
Treating all payroll as fixed when some wages vary directly with production or sales activity.
Including the same cost in both variable costs and fixed costs.
Using gross revenue in one month but costs from a different month.
Assuming a contribution margin ratio will stay constant when the sales mix or pricing changes.
Related Formulas
Frequently Asked Questions
What is the formula for monthly contribution margin?
Monthly contribution margin equals monthly sales revenue minus monthly variable costs.
How do you calculate the contribution margin ratio?
Divide contribution margin by monthly revenue, then multiply by 100. For example, a $20,000 margin on $50,000 of revenue produces a 40% ratio.
How is monthly break-even sales calculated?
Divide monthly fixed costs by the contribution margin ratio expressed as a decimal. A 40% ratio is entered as 0.40 in the break-even formula.
Is contribution margin the same as profit?
No. Contribution margin is before fixed costs. Estimated operating income is calculated after subtracting the fixed costs included in the calculation.
Can the contribution margin ratio be negative?
Yes. It is negative when variable costs are greater than revenue, meaning each additional sale creates a loss before fixed costs.
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