Contribution Margin Calculator

Contribution margin is what remains from the selling price after the costs that vary with each unit sold: product cost, fulfillment, transaction fees, per-sale commissions. It is the amount each sale contributes to fixed costs and, once they are covered, to profit. Sales managers, e-commerce teams and founders use it to judge promotions, discounts, channels and product mix, because it shows how much a decision changes the money available after variable costs. It is not net profit.

Unit contribution = unit selling price − variable cost per unit. It is a currency amount per unit. With a price of 100 and variable costs of 65, each unit contributes 35.

Contribution margin ratio = unit contribution ÷ unit selling price × 100. It expresses the same result as a share of the price, which makes products with different prices comparable. The ratio requires a price above zero.

Total contribution = unit contribution × units sold, for the period you choose. The calculator also shows total revenue (price × units). Prices and costs are excluding VAT, in one currency, and refer to the same period and the same channel.

What each term means

Unit sale price

Unit price used for contribution calculations.

Where to find it: The net price actually received per unit, excluding VAT and after the discounts or rebates you grant. For a channel with platform commissions, you can use the price paid by the customer here and put the commission in variable costs.

Variable cost per unit

Per-unit cost which increases with units delivered.

Where to find it: All costs that rise with each unit sold: purchase or production cost, packaging, shipping and handling, payment or marketplace fees, per-sale commissions, and an allowance for refunds if you track one per unit. Exclude rent, salaries and other fixed costs.

Units sold

Number of units actually or hypothetically sold.

Where to find it: Units sold, or planned to be sold, in the period you analyse. Use the same period as any fixed costs you will compare the total with.

Contribution per unit

Unit selling price minus per-unit variable cost.

Contribution margin ratio

Unit contribution divided by unit selling price.

Total contribution

Unit contribution × units sold.

Hypothetical example: a product sells for 100 excluding VAT, its variable costs add up to 65 per unit (product, shipping, payment fees and commission), and 100 units are sold in the month.

1. Contribution per unit100 − 65 = 35
2. Contribution margin ratio35 ÷ 100 × 100 = 35%
3. Total contribution35 × 100 = 3,500

Contribution per unit = 35

Unit contribution = 100 − 65 = 35. Contribution margin ratio = 35 ÷ 100 × 100 = 35 %. Total contribution = 35 × 100 = 3,500 for the month, on revenue of 10,000. If a 10 % discount brought the price to 90 with the same variable costs, unit contribution would fall to 25, and 140 units (3,500 ÷ 25) would be needed to keep the same 3,500 total.

Hypothetical numbers, used to show the calculation. Not real company data.

Use it before launching a promotion or accepting a discount request, to see how much each unit will still contribute. It is also the starting point of a break-even calculation: fixed costs divided by unit contribution give the units needed to cover them.

It helps compare channels. The same product can sell at the same price on your website, through a marketplace and through a distributor, yet leave very different contribution once commissions, fees and shipping are counted.

Use it for product mix decisions as well. When capacity, stock or sales time is limited, the products with the highest contribution per unit (or per hour of sales effort) usually deserve priority, even if their gross margin looks similar to others.

Gross margin subtracts the cost of goods from the price. It leaves out costs that also rise with every sale: shipping, packaging, payment and marketplace fees, commissions to sales staff or affiliates. For a decision that changes the number of units or the channel used, those costs matter as much as the product cost.

Take a hypothetical product sold at 100 with a product cost of 50: gross margin is 50 %. If shipping, fees and commission add another 15 per unit, contribution is 35, a 35 % ratio. A 20 % promotion takes the price to 80: gross margin falls to 37.5 %, which still looks comfortable, but unit contribution falls to 15 and the ratio to 18.75 %. To earn the same total contribution, you would need to sell more than twice as many units (35 ÷ 15 ≈ 2.33 times).

The same logic applies to channels. A marketplace that charges a commission per sale and a distributor that needs a lower price can show the same gross margin as your direct sales while leaving much less contribution. Contribution margin puts those costs on the table before the decision, not after.

A positive unit contribution means each additional sale helps cover fixed costs. A negative one means each sale loses money before fixed costs, so selling more makes the result worse.

The ratio tells you how much of each unit of revenue is left after variable costs. A higher ratio makes a business less sensitive to volume drops but more sensitive to price cuts in absolute amounts.

Total contribution is the amount available to pay fixed costs for the period. Compare it with those fixed costs, or use the break-even calculator, to know whether the period is profitable.

Practical levers

• Protect the net price: limit discounts and replace some of them with added value that costs little.
• Reduce variable costs that are often overlooked, such as shipping, packaging, payment fees and returns.
• Steer sales toward channels and products with higher unit contribution.
• Set a minimum unit contribution for promotions and check every promotion against it.
• Review commission plans so that they reward contribution, not only revenue.

Common mistakes

• Using only the purchase cost as variable cost and forgetting fulfillment, fees and commissions.
• Including fixed costs, such as rent or salaries, in the variable cost per unit.
• Calling total contribution profit while fixed costs have not been deducted.
• Using a list price when customers actually pay a discounted price.
• Mixing VAT-inclusive prices with costs excluding VAT.

Scenario comparison

The conservative case lowers the price by 5 %, raises the variable cost by 5 % and lowers units by 10 %; the optimistic case does the opposite. These are illustrative sensitivities, not forecasts.

Price and variable cost act on every unit, so when unit contribution is small compared with the price, a few percent on either one changes the result much more than the same percentage on volume.

The calculator assumes a constant price and a constant variable cost per unit over the period. Volume discounts, tiered fees or price changes need separate calculations.

Classifying a cost as fixed or variable is a judgement that depends on the horizon: some costs are fixed in a month but variable over a year.

Contribution does not include fixed costs, financing, taxes on profit or one-off expenses. It is a step toward profit, not profit.