How to Calculate Break-Even CPA for Shopify

Find the acquisition limit for one order

Break-even CPA equals average net order revenue minus average variable costs before advertising. CPA stands for cost per acquisition. In this calculation, the acquisition is a purchase. At your break-even CPA, an average order covers its variable costs and advertising. Any fixed overhead still needs to be paid.

Start with recent orders that look like the purchases you expect from the campaign. For a UK store, put every input in GBP. Divide revenue and costs by the same number of orders. Use merchandise revenue after discounts and refunds, plus any net shipping income you keep. Keep taxes collected on behalf of authorities outside this revenue figure. Shopify describes what its net sales figure includes.

Add product costs, fulfillment, payment fees, and incremental return costs. If you use actual net sales, reflect the refund reduction once. Use a separate allowance when modeling future orders with an order value that still includes expected refunds.

A worked example in pounds

Consider these illustrative inputs for a paid order. The store’s £72 order value already reflects discounts, but it uses a separate £3 allowance for expected losses from future refunds.

The break-even CPA is £32. To keep £8 per order after ads and before fixed overhead, set a target CPA of £24. Use the same revenue basis for the corresponding ratios. Break-even ROAS is £72 ÷ £32 = 2.25×. Target ROAS is £72 ÷ £24 = 3.00×.

Turn a weekly budget into a purchase target

Divide planned ad spend by target CPA and round up. With a £720 weekly budget and a £24 target, the plan needs at least 30 purchases. At the £32 break-even CPA, at least 23 purchases would cover spend on this model.

Suppose Meta reports 27 purchases after the campaign spends the full £720. The attributed CPA is £26.67. That falls between the break-even and target limits, leaving about £5.33 per order on the modeled cost and revenue basis. The useful next question is whether the actual paid order mix supports that estimate. Review the product mix, discounts, and fulfillment costs for the period.

When the budget changes, run the purchase math again. A higher budget raises the number of purchases needed at the same target CPA. The calculation sets a coverage threshold. It cannot predict conversion volume.

Recalculate before running a promotion

Imagine a promotion reduces average order revenue from £72 to £64.80, with the same modeled £40 of unit costs. Contribution falls to £24.80. To keep the same £8 per order after ads, the target CPA drops to £16.80. A campaign can keep delivering purchases at its old CPA while the promotion changes what each purchase is worth.

Set a new target when prices, supplier invoices, product mix, refunds, or shipping charges move materially. For a campaign built around one discounted product, start with that product’s economics before using the store-wide average. If the model leaves no room for paid acquisition, check costs and offer economics before increasing its budget.

Use Meta purchases as one check

In Ads Manager, start with spend and the website purchase metric for the selected account and reporting window. Meta’s reported purchase value depends on its attribution settings. Use the same reporting definition for both periods when comparing a change. See Meta’s Ads Insights reference.

Use the Profit Inspector break-even ROAS calculator to run your own numbers in GBP. Then use the ad spend review blueprint to check an actual week before using the new target.

Common questions