Break-even ROAS: how to calculate it (and why CRO lowers it)

ROAS stands for return on ad spend. It's the revenue your ads bring in, divided by what you paid for them. Google's own help page on Target ROAS uses this example: $5 in sales for every $1 in ad spend is a ROAS of 500%, which most store owners write as 5.0 or 5x.

The catch: ROAS counts revenue, not profit. A ROAS of 3 sounds great, but if costs eat 70% of every order, each ad sale loses money.

That's where break-even ROAS comes in. It's the ROAS where the profit from an order exactly covers the ad cost to get it. Above it, your ads make money. Below it, they cost you money. Shopify's guide to target ROAS calls it "the absolute floor where your business makes zero profit but loses no money on its acquisition marketing."

The formula is short:

Shopify's guide uses the same formula and is clear that the margin is the one you have before any ad costs. Here's how it works on a simple store. An average order is $50. The product costs $15. Shipping and packing cost $8. Payment and app fees take 4%, or $2. That leaves $25 to pay for the ad and keep as profit.

So this store needs at least $2 in sales for every $1 it spends on ads. The $25 is also your break-even cost per order (break-even CPA): the most you can pay in ads to get one order without losing money.

Put in your own numbers. Use averages per order from the last 30 to 90 days.

Write the number down. It's the floor for every campaign you run.

Include every cost that comes with one more order. Leave out costs you'd pay anyway.

Rent, salaries and monthly app plans don't change with one more order, so they stay out of break-even ROAS. They still need paying, which is why break-even is a floor, not a goal.

There's no single good number, because it depends on your margin. A ROAS of 2.5 is a great result for a store with a 60% margin and a loss for a store with a 30% margin. Here's how margin sets the floor:

So a good ROAS is one comfortably above your break-even, with enough room left to pay your fixed costs and keep a profit. Many store owners set a target ROAS a bit above break-even and use that as the number in Google Ads or Meta.

One exception: if your customers buy again, a first order can be worth more than its own profit. Some brands accept a first-order ROAS below break-even to win a customer. Only do that if you know, from your own data, how many first-time buyers come back.

Ad platforms report the revenue they think their ads caused, and 2 platforms can both take credit for the same order.

That's why many stores also track blended ROAS, also called MER (marketing efficiency ratio). Shopify's guide to MER defines it as total revenue ÷ total marketing spend, and notes it's also called blended ROAS. Its example: $200,000 in revenue on $50,000 of marketing spend is a MER of 4.

Most stores try to fix ROAS inside the ad account. But 2 numbers on your store decide how much an ad can cost before it loses money: your average order value and your conversion rate. Conversion rate optimization (CRO) works on both.

Some costs don't grow with the order. Shipping a box with 2 items often costs about the same as a box with 1. So when the order gets bigger, more of each dollar is left over, your margin goes up and your break-even ROAS goes down.

The ROAS drop looks small. The bigger win is in the profit column: at a $60 order, you can pay up to $31.60 for a sale instead of $25.

Top stores work hard on order size. Of the 25 top stores we broke down page by page, 22 suggest an upsell or cross-sell before checkout, and 19 do it right in the cart. Black Rifle Coffee does both in the same cart drawer:

A free shipping goal works the same way. Bodybuilding.com shows a progress bar in the cart, one of only 2 of the 25 stores that do:

Set the threshold with care, because free shipping moves your costs too. Our guide on how to set your free shipping threshold walks through the math.

To be precise: conversion rate doesn't change the break-even line itself. That's set by your margin. What it changes is the ROAS you actually get. You pay for clicks, so when more of those clicks buy, the same ad spend brings in more sales.

Going from 2% to 2.5% turns a campaign that only breaks even into one that makes $125 on every $500 you spend. Put both levers together, a 2.5% conversion rate and a $60 order, and the same 1,000 clicks return a ROAS of 3.0 against a break-even of 1.90, for $290 of profit instead of $0.

Both levers meet in one number: revenue per visitor, which is conversion rate × average order value. Multiply it by your margin before ads and you get the most you can afford to pay per click. Raise revenue per visitor and every ad you run has more room.

Most store owners try to fix a bad ROAS inside the ad account. But the ad's only job is to bring someone to your store. If the page they land on doesn't sell, no audience or bid will fix that.

This is the work we do every day at FunnelSpark, an ecommerce CRO agency for Shopify stores. Of the 1,000+ A/B tests we've run, 37% beat the original, against an industry average of about 15%. Not sure where your store leaks? Our free Leak Finder walks you through 20 checks from homepage to checkout.