Short answer: How do you calculate profit per order in e-commerce? You subtract product cost, shipping, the payment fee, and packaging and handling cost from the sale price, then adjust for the return rate. What remains is the contribution margin, and it shows the most you can pay for ads per order. Subtract the ad cost per order from the contribution margin and you get net profit. Break-even ROAS is the sale price divided by the contribution margin. Rebel Co. Group built this tool so you can steer your ad budget toward the products that make money.
Enter product cost from your supplier invoice, and write the sale price as the amount the customer pays including VAT, and remember to subtract VAT separately. Take shipping cost from the dimensional weight brackets in your carrier contract, and the payment fee from your payment processor statement or from the dashboard of a provider such as Stripe or PayPal. Find the return rate by dividing the number of orders returned in the last 90 days by total orders in your e-commerce panel. For ad cost per order, divide total spend in Google Ads and Meta Ads Manager by the number of orders that came from ads only.
The calculator works with the values you enter. Your data stays in your browser and is never sent to a server. Results support decisions and do not replace accounting records.
Formula
Contribution margin is what an order leaves after all of its variable costs are paid, and it sets the ceiling for every growth decision, ads included.
- Payment fee = Sale price x Payment processing fee rate
- Contribution margin = (1 - Return rate) x (Sale price - Product cost - Payment fee) - Shipping - Packaging and handling
- Contribution margin % = Contribution margin / Sale price x 100
- Net profit per order = Contribution margin - Ad cost per order
- Break-even CAC = Contribution margin, which is the most you can pay for ads per order
- Break-even ROAS = Sale price / Contribution margin
Why is the return adjustment built this way? On a returned order the sales revenue goes back to the customer, the product goes back to the warehouse, and with most providers the payment fee comes back. Shipping and packaging, however, are gone, since they were spent on every order. That is why the first three items are multiplied by the "retained order" rate, while shipping and handling are subtracted in full. The calculator uses this simplified model, and if you pay for return shipping separately, add it to the shipping field.
Worked example
Let us calculate a product that sells for 60 USD, with a product cost of 25 USD, shipping of 5 USD, a 2.5% payment fee, packaging and handling cost of 1.50 USD, an 8% return rate and an ad cost of 10 USD per order.
| Step | Calculation | Result |
|---|---|---|
| Payment fee | 60 x 2.5% | 1.50 USD |
| Retained order margin | 0.92 x (60 - 25 - 1.50) | 30.82 USD |
| Contribution margin | 30.82 - 5 - 1.50 | 24.32 USD (40.5%) |
| Net profit per order | 24.32 - 10 | 14.32 USD |
| Break-even CAC | Contribution margin | 24.32 USD |
| Break-even ROAS | 60 / 24.32 | 2.47x |
If the return rate rose from 8% to 20%, contribution margin would fall to 20.30 USD and net profit to 10.30 USD. Returns are the item that quietly eats margin.
Here is how to read it: for this product you can pay up to 24 USD of ads per order, you pay 10 USD, and the 14 USD in between is profit. As long as your campaign ROAS stays above 2.47x, every order makes money. If you sold the same product with a 10 USD discount, contribution margin would fall to 15.35 USD and break-even ROAS would rise to 3.26x, so a discount takes away from ad efficiency too.
How to read the result
If contribution margin is below 30%, the product cannot be grown with ads, between 30% and 45% it calls for careful scaling, and above 45% it leaves room for aggressive growth.
These thresholds are not hard rules, they are common behavior we see in practice. On low-margin products, net profit per order comes close to zero once ad cost is added, and a single bad week can turn the month into a loss. When you read break-even ROAS, look at the industry reference: according to reports, the median Google Ads ROAS is about 3.3x and the median Meta Ads ROAS about 2.2x. If your break-even ROAS goes above 3x, selling profitably on Meta gets hard, and the product needs a fix on either the price or the cost side.
Turn contribution margin into a monthly goal as well. If your monthly fixed cost is 12,000 USD and your contribution margin per order is 24.32 USD, you need about 494 orders a month to break even. This number tells you the volume your ad budget has to carry, and it feeds straight into the ad budget calculator. If net profit per order is positive but monthly volume is below the break-even order count, the business still loses money, because unit profit is not enough to cover the fixed cost. Unit economics and monthly economics are two separate questions, so do not make a growth decision without answering both.
An ad budget is planned on contribution margin, not on revenue, because margin pays for ads, not revenue.
Common mistakes
- Mixing up VAT. If the sale price includes VAT and the product cost excludes it, the margin looks close to 20% higher than it really is. Keep both on the same basis or subtract VAT from the price.
- Not counting free shipping as a cost. Shipping is free for the customer, not for you. Even if you build the shipping fee into the price, it must stay as a separate item in the calculation.
- Loading fixed costs onto each order. Rent, salaries and software subscriptions do not go into contribution margin. Contribution margin is collected to cover these costs, and including them in the unit calculation distorts scaling decisions.
- Dividing ad cost across organic orders too. If you divide total ad spend by total orders, ad cost per order comes out low. The denominator should be only the orders that came from ads.
- Letting one product represent the whole catalog. Average margin changes when the product mix changes. Calculate your 10 best sellers one by one, then take the order-weighted average.
How to improve this number
- Lower the return rate. A size chart, real product photos and clear descriptions bring the return rate down by a few points, and every point goes straight into margin. The methods are in the guide to reducing return rates.
- Renew your carrier agreement. As your monthly shipment count grows, dimensional weight brackets become negotiable. Get quotes from two carriers and shrink the package size to lower the billable weight.
- Grow average order value. Shipping and handling cost are fixed per order, and as the cart grows, the share of these items shrinks. Start with the guide to raising order value.
- Negotiate the payment fee. As revenue grows, processing rates come down. Talk to your provider with a yearly volume commitment, and evaluate installment fees separately.
- Bring down ad cost per order. If repeat purchases grow through remarketing, email and WhatsApp, ad cost is divided over more orders. The guide to lowering CAC gives the roadmap.
- Steer ads to high-margin products. Feature products with a contribution margin above 45% in campaigns, and offer low-margin ones as complementary items. For the big picture see the unit economics, CAC and LTV guide, and for the break-even logic the break-even ROAS article.
Frequently asked questions
What is the difference between contribution margin and gross profit margin?
Gross profit margin only subtracts product cost from the sale price. Contribution margin also subtracts everything that varies per order, such as shipping, payment fees, packaging and returns. In e-commerce this difference is large, because shipping and fees can take 10-15% of the price. Use contribution margin for ad decisions, because gross margin makes you look more profitable than you are. In an accounting report people talk about gross margin, and in an ad plan they talk about contribution margin.
What is the most I can pay for ads per order?
As much as your contribution margin. If your contribution margin is 24 USD, you break even when you pay 24 USD of ads per order and you profit when you pay less. In practice, set your target at 50-60% of contribution margin so there is room for fixed costs and fluctuation. This value is your break-even CAC, and you can use it directly as the target CPA in Google Ads or the cost per result goal in Meta.
Do break-even ROAS and break-even CAC say the same thing?
They say the same truth in two different languages. Break-even CAC is the most you can pay for ads per order, and break-even ROAS expresses the same limit as a multiple of revenue. If the sale price is 60 USD and the contribution margin is 24 USD, break-even CAC is 24 USD and break-even ROAS is 2.5x. If you use target ROAS bidding in Google Ads, enter ROAS as the target, and if you use target CPA, enter CAC.
How should I factor in the return rate?
Divide the number of orders returned in the last 90 days by total orders and enter it as a percentage. The calculator adjusts sales revenue, product cost and fees with this rate and subtracts shipping and handling in full, because those items do not come back on a return. If return rates differ a lot by category, for example 25% in footwear and 3% in accessories, do a separate calculation for each category.
Should I add fixed costs to the profit calculation?
Not to the per-order calculation, but yes to the monthly one. Contribution margin is the pool that is collected to cover fixed costs. If your monthly fixed cost is 12,000 USD and your contribution margin per order is 24 USD, you need 500 orders a month to break even. Combine this number with the ad budget calculator and see the clicks needed to reach that volume. Mixing fixed costs into the unit calculation points ad decisions in the wrong direction.