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Guide · Break-Even

Weighted Contribution Margin: Units vs. Revenue

Calculate weighted contribution per unit and a revenue-weighted contribution ratio without mixing the two weighting systems.

By PriceAndProfit Editorial Updated 3 min read

On this page
  1. Worked calculation
  2. Decision checks and limits
  3. Apply the calculation

A product portfolio has two useful contribution averages: contribution dollars per unit and contribution as a percentage of revenue. The first uses unit weights; the second uses revenue weights. Mixing these bases produces an incorrect break-even model when products have different selling prices. Start by summing revenue and variable costs, then use weighted calculations as a reconciliation.

Worked calculation

Weighted contribution per unit = total contribution ÷ total units; weighted contribution ratio = total contribution ÷ total revenue

Suppose a business sells 300 units of product A at $20 with $12 variable cost, and 100 units of product B at $60 with $30 variable cost. A contributes $8 per unit and B $30. Total contribution is $2,400 plus $3,000, or $5,400. There are 400 units, so weighted contribution per unit is $13.50. The unit weights are 75% A and 25% B, giving 0.75 × $8 + 0.25 × $30 = $13.50.

Revenue is $6,000 for each product, totaling $12,000. A's contribution ratio is 40% of revenue and B's is 50%. Because each supplies half the revenue, the weighted contribution ratio is 45%. Applying the 75% and 25% unit weights to those ratios would produce 42.5%, which does not reconcile with $5,400 divided by $12,000. The more expensive product has a greater revenue weight than its unit count suggests.

Hypothetical worked example
ProductUnitsRevenueContributionUnit weightRevenue weight
A 300 $6,000 $2,400 75% 50%
B 100 $6,000 $3,000 25% 50%
Total 400 $12,000 $5,400 100% 100%

Decision checks and limits

For $4,500 of fixed costs, the continuous break-even estimate is $4,500 divided by $13.50, or approximately 333.3333 units at the assumed unit mix. The revenue estimate is $4,500 divided by 0.45, or $10,000. Both describe the same continuous mix. Real orders require whole units and may not match the exact ratio, so construct a feasible product basket and verify its actual contribution before claiming the rounded plan breaks even.

The weighted averages are valid only for the stated mix and cost behavior. If lower-priced A becomes a larger share of units, total contribution per unit and the revenue ratio both change. Discounts, returns, and order-level costs can also alter individual contribution. Do not carry a historical portfolio ratio into a forecast without checking whether future sales composition remains comparable. A total revenue denominator of zero makes the contribution ratio undefined, while zero total units makes the per-unit average undefined; neither case should be converted into a zero profitability result.

Apply the calculation

  1. Calculate product dollars

    Use realized price and the full defined variable cost to obtain revenue and contribution for each product.

  2. Match weights to the measure

    Use unit shares for contribution dollars per unit and revenue shares for contribution percentages.

  3. Test a changed mix

    Rebuild totals under a plausible shift toward a different product, then verify whole-unit feasibility for a break-even plan.

Method references: OpenStax: Contribution margin. Accessed October 22, 2026. All dollar figures are hypothetical worked examples.

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