Contribution Margin: Formula, Ratio & How to Calculate It

Contribution margin tells you how much of each dollar of revenue actually contributes to covering fixed costs and profit. Here's the formula, the ratio, and how ecommerce brands should use it.

Jakob Sperber

Director

Finance

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Contribution margin is the amount of revenue left after you subtract all variable costs. It's the money that contributes to covering fixed costs and generating profit. Without it, you're guessing on every pricing, marketing, and growth decision.

The Formula

Contribution Margin = Revenue − Variable Costs

Contribution Margin Ratio = CM / Revenue

Example: $500,000 revenue, $310,000 variable costs. CM = $190,000. CM Ratio = 38%. For every dollar of revenue, 38 cents contributes to fixed costs and profit.

Variable Costs vs Fixed Costs

Variable (scale with each order)

  • COGS: Raw materials, manufacturing, landed cost

  • Shipping/fulfilment: Pick, pack, postage, 3PL fees

  • Payment processing: Shopify Payments, Stripe, PayPal (1.5–3%)

  • Packaging: Boxes, mailers, inserts

  • Marketplace commissions: Amazon, eBay referral fees

  • Returns: Processing, restocking, write-offs

Fixed (don't change per order)

  • Rent, salaries, software subscriptions, insurance, professional services

For the full cost classification, see our ecommerce accounting guide.

CM Per Unit vs Total CM

Per unit answers: is this product worth selling? Use it for pricing decisions and product comparisons.

Total CM answers: can the business cover fixed costs and generate profit? Use it for budgeting and forecasting.

Product A: $15 CM/unit × 2,000 units = $30,000 total. Product B: $8 CM/unit × 5,000 units = $40,000 total. B is less efficient per unit but contributes more overall. Both perspectives matter.

The CM1 → CM2 → CM3 Waterfall

Standard contribution margin lumps all variable costs together. Ecommerce needs more granularity:

CM1: After COGS

CM1 = Revenue − COGS. Your product-level margin. Healthy DTC CM1: 60–80%. Below 50%? Fix pricing or COGS before anything else.

CM2: After All Variable Costs

CM2 = CM1 − Shipping − Fulfilment − Processing − Packaging − Returns. This is your true per-order margin before marketing. It determines how much you can spend on customer acquisition. Strong CM2: 40–55%. Below 30%? Scaling with paid acquisition becomes extremely difficult.

CM3: After Marketing

CM3 = CM2 − Marketing Costs. What's left to cover fixed costs and profit. If CM3 is negative, you're relying on repeat purchases to eventually recoup — valid strategy, but only if retention economics support it.

Full framework in our CM1, CM2, CM3 guide.

Why CM Matters More Than Gross Margin for Ecommerce

Gross margin = Revenue − COGS. It ignores shipping, processing, fulfilment — costs that can represent 15–25% of revenue for ecommerce.

Example at $80 AOV: COGS $24. Gross margin: $56 (70%). But add shipping ($9), processing ($2), fulfilment ($4), packaging ($1.50), returns ($3.50): CM2 = $36 (45%).

A 25-percentage-point gap. A brand making decisions on the 70% number will overspend on acquisition and wonder why the bank account doesn't match the "healthy" margins.

How to Improve CM

1. Reduce COGS

Negotiate with suppliers, bulk purchasing, reformulate, change suppliers.

2. Increase Prices

Most underused lever. A 10% price increase on 40% CM ratio improves per-unit CM by 25%. The volume drop required to offset that is usually smaller than brands expect.

3. Reduce Variable Costs

Negotiate shipping rates, reduce return rates (better sizing, descriptions, photography), optimise packaging.

4. Increase AOV

Many variable costs are per-order, not per-unit. Higher AOV spreads those costs across more revenue, improving your CM ratio.

CM and Pricing Decisions

If your CM is too thin, you have a pricing problem, not a marketing problem. If CM2 is 25%, there's barely room for customer acquisition. Even a brilliant campaign can't overcome broken unit economics.

Before spending a dollar on ads, know your CM2 per order. Then: how much can I afford to spend to acquire a customer? That question feeds directly into setting your ad budget from your P&L.

The Bottom Line

Track CM1 per product, CM2 per order, CM3 per channel, and CM ratio. If you only track one: make it CM2. It's the clearest indicator of whether your business can scale profitably or whether you need to fix the fundamentals first.

Start with a free profit audit.

Find out what's holding your profit back.

We look at your numbers, identify the primary constraint, and tell you exactly what we'd fix. No obligation. You keep the findings regardless.

Start with a free profit audit.

Find out what's holding your profit back.

We look at your numbers, identify the primary constraint, and tell you exactly what we'd fix. No obligation. You keep the findings regardless.

Start with a free profit audit.

Find out what's holding your profit back.

We look at your numbers, identify the primary constraint, and tell you exactly what we'd fix. No obligation. You keep the findings regardless.

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