What Is ROAS? Formula, Break-Even ROAS and Blended ROAS (MER)

ROAS (return on ad spend) is the revenue your ads brought in divided by what you spent on them. Put simply: how many dollars of sales came back for every $1 you put into ads. It is the number most Meta advertisers check first, and also one of the most misread, because the same campaign can show different ROAS figures depending on where you look. This guide covers the formula, how to work out your break-even ROAS from your margin, the difference between Meta-reported ROAS and blended ROAS (MER), and why Meta and Shopify rarely agree.

The ROAS formula

ROAS = purchase value ÷ ad spend

Purchase value is the revenue from the purchases credited to your ads. Ad spend is what you paid Meta for the same campaigns over the same dates. ROAS is usually written as a multiple, such as 3.20×, which means $3.20 in sales for every $1 spent. Some tools show the same thing as a percentage (320%). A ROAS of 1.00× means the ads brought back exactly what they cost in revenue. That is not the same as breaking even, as the margin maths below shows.

A worked example

The numbers in this example are illustrative. Say a Meta campaign spends $1,000 in a week, and Meta credits it with 40 purchases worth $3,200 in total.

• ROAS = $3,200 ÷ $1,000 = 3.20×
• Cost per purchase (CPA) = $1,000 ÷ 40 = $25
• Average order value (AOV) = $3,200 ÷ 40 = $80

The three are linked: ROAS is AOV divided by CPA ($80 ÷ $25 = 3.20). That helps when you diagnose a change. If ROAS falls, either each purchase cost more to win (CPA rose) or each order was worth less (AOV fell), and the fix is different for each: the first points at the ads and the audience, the second at your offer, bundles and pricing.

ROAS vs ROI

ROI (return on investment) measures profit, not revenue. For ads it is (gross profit − ad spend) ÷ ad spend. ROAS ignores what your products cost to make, pack and ship, so a high ROAS can still lose money.

Take the same example with a 40% gross margin, meaning $40 of every $100 in sales is left after product cost, shipping and payment fees. $3,200 in sales leaves $1,280 of gross profit. Subtract the $1,000 of ad spend and $280 is left: an ROI on the ad spend of 28%. Same campaign, ROAS of 3.20×, ROI of 28%. With a 25% margin the gross profit would be $800 and the campaign would lose $200, at exactly the same 3.20× ROAS.

Break-even ROAS: what “good” means for your store

Break-even ROAS is the ROAS at which the ads pay for themselves on the first order, with nothing left over. It comes straight from your margin:

break-even ROAS = 1 ÷ gross margin

With a 40% margin, break-even ROAS is 1 ÷ 0.40 = 2.50×. Every $1 of ads has to bring back $2.50 in sales, because only $0.40 of each sales dollar is available to pay for the ad. Above 2.50× the campaign makes money on the first purchase; below it, it loses money unless those customers buy again.

This is why there is no single “good ROAS”. A target that ignores margin means nothing: 2.00× loses money for a store with a 30% margin and makes a healthy profit for one with a 75% margin. Work out your own break-even ROAS, then set a target above it that covers your fixed costs and the profit you want.

Two refinements make the number more honest. First, use a margin that includes every cost that grows with each order (product, packaging, the shipping you pay, payment fees, average discounts), not just the product cost. Second, if customers reliably come back, the first order does not have to carry the whole cost of winning them. The cohort retention grid on PixlBridge's Shopify page (do customers come back?) shows how often they do.

Meta-reported ROAS vs blended ROAS (MER)

There are two common ways to calculate ROAS, and they answer different questions.

Meta-reported ROAS uses the purchase value Meta credits to your ads: purchases by people who clicked or saw an ad within the attribution window. Meta reports it per campaign, ad set and ad, so it is the right number for comparing them with each other and for moving budget.

Blended ROAS uses all your store revenue: total sales ÷ total ad spend. It is also called MER (marketing efficiency ratio). It does not depend on attribution, so it cannot be inflated by Meta taking credit for a sale another channel made. But it also counts sales your ads had nothing to do with: repeat customers, email, organic search. It is the right number for “is advertising working for the business as a whole?”

Strictly, MER divides revenue by all marketing spend. If you advertise on more than one platform, add every platform's spend when you calculate MER for the whole business.

Use both. Blended ROAS tells you whether the whole system is profitable; Meta-reported ROAS tells you which parts of the account to scale and which to cut. If Meta-reported ROAS rises while blended ROAS falls, check whether Meta is taking credit for sales that would have happened anyway.

Why Meta-reported ROAS and Shopify revenue differ

Put Meta's purchase value next to Shopify's sales for the same week and they almost never match. The usual reasons:

• Attribution windows. Meta credits a purchase to an ad when it happens within a set time after a click on, or a view of, that ad. The default for most ad sets is 7-day click and 1-day view; Ads Manager shows each ad set's setting. A shopper who saw an ad, scrolled past and bought the next day from an email can be counted by Meta and by your email tool.
• Different dates. The two systems can put the same order on different days, so a short date range can disagree even when a whole month lines up better.
• Missed events. When an ad blocker or the browser's privacy protection stops the Meta Pixel, Meta never hears about the purchase and Meta-reported ROAS is understated. Sending purchases from a server through the Conversions API means the browser no longer decides whether a purchase reaches Meta; see Meta Pixel vs Conversions API.
• Estimated conversions. Meta may include conversions it models statistically where it cannot observe them directly.
• Refunds and cancellations. A Purchase event sent to Meta is not taken back when the order is refunded, while Shopify's net sales go down.
• What counts as value. The value sent with a Purchase event may include or exclude tax and shipping depending on the setup, and Shopify reports gross, net and total sales separately.

None of this means one number is right and the other wrong. They measure different things. Decide which number answers your question, and compare it with itself over time.

How PixlBridge shows ROAS

• Home: Blended ROAS. Your Shopify store revenue for the period divided by your Meta ad spend, shown as a multiple (for example 3.20×) with the plain line “$3.20 back for every $1”, a verdict word and the change from the period before. Next to it are the two numbers it is built from: Revenue and Ad spend. When no store is connected, the card shows Meta's own figure instead.
• Ads page: ROAS. Meta-reported ROAS (purchase value ÷ ad spend, as Meta counts it) for the account and for every campaign, ad set and ad, next to Purchases, Purchase value and Cost per purchase (CPA). Creatives can be ranked by ROAS, which is often a different order from ranking them by CTR.
• Purchases sent to Meta (CAPI). PixlBridge sends each Shopify order to Meta through the Conversions API, so Meta-reported ROAS is not limited to the purchases a browser pixel managed to see.

Read the Blended ROAS on Home against your break-even ROAS, not against the verdict word alone. The verdict is a quick read; only your margin tells you whether a given ROAS makes money.

Summary

ROAS is purchase value ÷ ad spend. On its own it says nothing about profit, so compare it with your break-even ROAS (1 ÷ gross margin). Use Meta-reported ROAS to compare campaigns, ad sets and creatives, use blended ROAS (MER) to judge advertising as a whole, and expect the two to differ for the reasons above. The Facebook ads metrics glossary covers the metrics around ROAS, such as CPA, CPM and CTR, and PixlBridge for Meta ads shows how the numbers come together in one dashboard.