Contribution Margin in eCommerce: Definition and Formula
- Contribution margin is order value after discounts minus variable costs: cost of goods, payment fees, fulfilment and shipping you pay, and a returns provision.
- There are two versions. Before ads it sets what you can afford to spend. After ads it shows what the order really kept.
- Gross margin subtracts only cost of goods, so it overstates what an order earns.
- Break-even ROAS is one divided by contribution margin before ads, so no ROAS target is safe without it.
- Compute it per order and per product. A blended store average hides the products that lose money.
- Contribution margin leaves out fixed overheads such as rent and salaries. True Profit adds the customer view on top.
Contribution margin ecommerce teams track is what an order has left once you pay for everything that order caused. The product, the postage, the card fee and the refund risk all come out. The rest pays for your fixed costs and, if you are lucky, leaves profit. Last updated: November 2026.
I see this number missing when teams argue about ad targets. Brands know their revenue and their ROAS. Fewer can say what an average order keeps. Omniconvert Commander (formerly Nexus) is the AI eCommerce growth engine for Shopify brands. It unifies your store, ad and customer data and ranks growth opportunities by profit impact. You approve what goes live.
Below you get the definition and the formula. For the full comparison of ROAS, MER, POAS and True Profit, read the True Profit vs ROAS complete guide.
What is contribution margin ecommerce brands use?
Contribution margin is defined as order value after discounts minus the variable costs of winning and fulfilling that order. A variable cost is a cost that grows with each order. Rent and salaries do not, so they stay out. They are paid from the margin the orders contribute.
What is the contribution margin formula?
Contribution margin after ads is the same number as True Profit.
The two versions answer two questions. Contribution margin before ads is defined as the margin an order has available to pay for its own advertising. It tells you how much you can spend to win an order. Contribution margin after ads is defined as what the order kept once the advertising is paid. It tells you whether you won anything.
An illustrative order shows both. The order is $100 after discounts. Cost of goods is $35, shipping you pay is $8, payment fees are $3 and a returns provision is $5. Contribution margin before ads is $49, or 49%. The ads that won the order cost $30, so contribution margin after ads is $19, or 19%.
What is the difference between contribution margin and gross margin?
| Measure | What it subtracts | Illustrative result |
|---|---|---|
| Gross margin | Cost of goods ($35) | $65, or 65% |
| Contribution margin before ads | Cost of goods, shipping ($8), fees ($3), returns ($5) | $49, or 49% |
| Contribution margin after ads | All of the above plus ad spend ($30) | $19, or 19% |
| What it does not subtract | Rent, salaries, software | Paid from the margin above |
The gap between the first and second rows is where brands go wrong. Gross margin is the figure sitting in the accounts, so it becomes the figure used to set ad targets. In an illustrative case, a team sees 65%, works out that a ROAS near 1.5 breaks even, and runs campaigns at 1.8 with a clear conscience. Against a contribution margin of 49%, break-even is about 2.0. Every one of those campaigns loses money on each order, and the dashboard shows green the whole time. The cost is not one bad month. It is months of scaling the wrong campaigns because the target looked safe.
How do you read contribution margin per order and per product?
The per-order view includes costs the product does not carry: a free-shipping threshold, a discount code, a payment fee on a larger basket. Two orders of the same product can differ by tens of percentage points. Use this view to judge offers and thresholds.
The per-product view uses the order lines. Take two illustrative products, both sold at $100. One has a contribution margin before ads of 60% and rarely comes back. The other has 30% because it is heavy, costly to ship and returned often. The store average, with equal sales of each, is 45%, and it describes neither product. Ads for the second one need half the room to spend. For the cost-of-goods input, see the cost of goods sold formula. To test your own numbers before a sale, use the Black Friday margin calculator.
Why is contribution margin the floor under your ROAS target?
ROAS is revenue divided by ad spend. It ignores every cost between the sale and your bank account, so it cannot tell you where profit starts. The contribution margin supplies that point. Take the illustrative 49% order: one divided by 0.49 is about 2.0, and that is the lowest ROAS that does not lose money. Profit, and a share of overheads, only begins above it.
Contribution margin before ads, divided by ad spend, is POAS, covered in what is POAS. For the side-by-side of the two measures, see POAS vs ROAS. True Profit takes the next step, and the definition of True Profit in eCommerce explains it.
Omniconvert Commander uses the cost data you connect to show contribution margin after ads for each ad. You approve what goes live.
Contribution margin in eCommerce: FAQs
What is contribution margin in eCommerce?
The amount an order has left after its variable costs: cost of goods, payment fees, fulfilment, shipping and returns. What remains pays for fixed overheads and profit.
What is the contribution margin formula?
Order value after discounts, minus cost of goods, payment fees, fulfilment and shipping you pay, and a returns provision. Subtract ad spend as well for the version after ads. Divide by order value for a percentage.
What is the difference between contribution margin and gross margin?
Gross margin subtracts only cost of goods. Contribution margin also subtracts payment fees, fulfilment, shipping and returns. It is always lower, and it is the number that tells you what an order earns.
Should contribution margin include ad spend?
Use both. Before ads, it sets how much you can afford to spend to win an order. After ads, it shows what the order kept. Label which one you mean.
How does contribution margin set a ROAS target?
Break-even ROAS is one divided by contribution margin before ads, written as a fraction. For example, a 50% margin breaks even at a ROAS of 2.0. Any target below that loses money.
Does Omniconvert Commander calculate contribution margin?
It measures True Profit per ad, which is contribution margin after ads. Omniconvert Commander uses the cost data you connect to show contribution margin after ads for each ad. You approve what goes live.
Know what an order keeps
Contribution margin is the number between revenue and profit. Calculate it before ads to set your ROAS floor, and after ads to see what you kept. Use it per order and per product, never as one store average. Then judge every campaign against that floor instead of against the gross margin in your accounts.