What is contribution margin?
Contribution margin is what's left from a sale after you pay the variable costs of making it. For an online brand that means product cost, fulfilment, payment fees, returns and the marketing spent to win the order. It tells you how much each sale contributes towards your fixed costs and, eventually, profit. A business can grow revenue fast while every order loses money; contribution margin is how you spot it.
The contribution margin formula
- Contribution margin = revenue − variable costs
- Contribution margin per unit = selling price − variable cost per unit
- Contribution margin ratio = contribution margin ÷ revenue × 100
Variable costs rise and fall with each sale. Fixed costs, such as rent, salaries and software, don't. Contribution margin deliberately leaves fixed costs out, so you can see the economics of each sale on its own.
A worked example for an online brand
Many ecommerce and D2C brands break contribution into three levels, often called CM1, CM2 and CM3. Here's an example order, excluding VAT:
- Order value: £60.00
- Less product cost (£21.00) → CM1 = £39.00 (65%)
- Less fulfilment and delivery (£6.00), payment fees (£1.20) and a returns allowance (£3.00) → CM2 = £28.80 (48%)
- Less marketing to win the order (£18.00) → CM3 = £10.80 (18%)
A 65% product margin looks healthy. After everything that actually varies with the order, this sale contributes £10.80. If marketing per order crept up to £30, the same order would lose money, even though revenue looks identical.
Contribution margin vs gross margin vs net profit
- Gross margin takes off only the cost of goods. It's close to CM1.
- Contribution margin also takes off every other cost that scales with sales. CM3 is the truest view of whether growth pays.
- Net profit takes off fixed costs too. It's the bottom line for the business, not for each order.
How contribution margin fits with unit economics
Unit economics look at the profit or loss on one order or one customer. Alongside contribution margin, the numbers that matter most for consumer brands are:
- Customer acquisition cost (CAC): what you spend on marketing to win a new customer.
- Customer lifetime value (LTV): the total contribution a customer generates over their relationship with you, not just their first order.
- Payback period: how long it takes a customer's contribution to cover what it cost to acquire them.
A first order that only breaks even can still be a good investment if customers come back. That's why retention and repeat purchase sit at the heart of profitable growth. A commonly used rule of thumb is to aim for lifetime value at least three times acquisition cost, but your payback period and cash position matter just as much.
How to improve contribution margin
- Raise order value with bundles, multipacks and sensible free-delivery thresholds.
- Discount with discipline. Blanket promotions often buy revenue at a loss.
- Cut returns with better product information, sizing and imagery.
- Lower fulfilment costs through packaging, carrier mix and delivery options.
- Improve conversion, so the same marketing spend wins more orders.
- Choose channels by contribution, not revenue. Marketplace fees and creator commissions change the maths.
Not sure where your business is leaking? Our free 2-minute Growth Diagnostic finds your biggest leak — acquisition, conversion, retention or value — or see how we build growth strategy around the numbers that actually pay.