Is CPA the same as CAC?

They are close but not identical. CPA usually means ad spend per conversion inside one campaign or channel. Customer acquisition cost, or CAC, often includes all marketing and sales costs divided by new customers, so it is usually higher and broader.

Why is my CPA higher in the store than in the ad platform?

Ad platforms count conversions by their own attribution rules and may include modelled results, while your store counts real orders. Tracking gaps, browser privacy settings and different attribution windows explain most differences. Use store orders to confirm true profitability.

Cost per acquisition (CPA)

Cost per acquisition (CPA) is the average ad spend needed to win one conversion, such as a purchase or sign-up, calculated as spend divided by conversions.

What is CPA?

Cost per acquisition, or CPA, tells you how much you pay in advertising to get one result. In e-commerce the result is usually a purchase, so CPA is often called cost per purchase. Some teams use it for sign-ups, leads or app installs instead. CPA matters because it connects ad spend directly to customers. If you know how much profit one order makes, you can compare it to CPA and see straight away whether a campaign earns or loses money. It is one of the main numbers ad platforms like Meta and Google let you optimise toward and report on.

How to calculate CPA

Divide total ad spend by the number of conversions in the same period. For example, if a campaign spends $600 and brings in 20 purchases, the CPA is 600 divided by 20, which is $30. If you then improve the ad and get 30 purchases for the same $600, the CPA drops to $20. Be clear about which conversions you count. Platform-reported purchases can differ from orders in your store because of attribution windows and tracking gaps. Many teams track both numbers, using the platform figure for daily decisions and store orders to check the real result.

What is a good CPA?

A good CPA is one below the profit you make on a customer, so there is no single number that fits every store. Start with your break-even CPA: the price of the product minus product cost, shipping, payment fees and other per-order costs. If a product sells for $50 and those costs total $22.75, you have $27.25 left, so any CPA under $27.25 is profitable on the first order. If customers often buy again, you may accept a higher CPA on the first order. CPA typically varies a lot by niche, price point and season, so compare against your own margin rather than general benchmarks.

How to improve CPA

Improve the ad first: test new hooks, angles and formats, because creative usually has the biggest effect on cost. Make sure the landing page matches the ad and loads fast, since a better conversion rate lowers CPA directly. Raise average order value with bundles or a sensible free shipping threshold, which does not lower CPA itself but makes a higher CPA affordable. Give campaigns enough budget and time to exit learning before judging them. Cut ads and audiences that consistently cost more than break-even, and move budget to the ones that stay below it.

CPA vs ROAS

CPA measures cost per conversion in money, while return on ad spend, or ROAS, measures revenue per dollar of ad spend. ROAS is revenue divided by ad spend. A campaign with a $30 CPA on a $60 average order has a ROAS of 2. CPA is easier to use when every order is worth about the same, such as a single product store. ROAS is more useful when order values vary a lot, because a campaign bringing fewer but larger orders can look worse on CPA yet better on ROAS. Many advertisers watch both.

Free tool: Break-even ROAS Calculator

Questions

Is CPA the same as CAC?: They are close but not identical. CPA usually means ad spend per conversion inside one campaign or channel. Customer acquisition cost, or CAC, often includes all marketing and sales costs divided by new customers, so it is usually higher and broader.
Why is my CPA higher in the store than in the ad platform?: Ad platforms count conversions by their own attribution rules and may include modelled results, while your store counts real orders. Tracking gaps, browser privacy settings and different attribution windows explain most differences. Use store orders to confirm true profitability.