How to Calculate ROAS: The Formula, Your Break-Even, and Three Ways the Number Lies

Your ad account shows a ROAS of 4.2. Your P&L for the same month shows a loss. Both numbers are correct. They just answer different questions.

The contradiction resolves through four calculations: the ROAS formula itself, a worked example with gross and net revenue, break-even ROAS by margin, and three cases where the dashboard number shows something different from what the business actually made.

What is ROAS?

ROAS (return on ad spend) is the ratio of revenue generated by ads to money spent on ads. €12,000 in revenue from €3,000 in ad spend is a ROAS of 4.0.

Meta and Google show platform ROAS in your dashboard: revenue each platform credits to itself, based on its own attribution model. A blended view instead uses your actual total revenue from Shopify or your ERP, summed across every channel. The two numbers often diverge sharply, more on that in the channel silo section below.

The formula and an honest example

ROAS = revenue ÷ ad spend. That part takes three seconds. The trap sits inside revenue: Shopify and the ad platforms usually report it gross, including VAT (19% in Germany). What you actually earn is net.

€12,000 gross is €10,084 net (12,000 ÷ 1.19). The 4.0 in your dashboard becomes 3.4 once you calculate net (10,084 ÷ 3,000 = 3.36). Steer your account toward a net target using gross ROAS, and you'll be off by 19%, systematically.

ROAS, ROI, MER: three numbers, three jobs

All three run on the same underlying numbers and still answer different questions.

• ROAS: revenue ÷ ad spend. Runs your campaigns, checked daily.
• ROI: profit ÷ investment. Investment counts every cost: ads, cost of goods, shipping, fixed costs. Example: €12,000 in revenue, €3,000 in ads, €6,500 in cost of goods, shipping, and fixed-cost allocation leave €2,500 in profit. Investment totals €3,000 plus €6,500, or €9,500, so ROI = 2,500 ÷ 9,500 = 26%. A ROAS of 4.0 and an ROI of 26% describe the same campaign.
• MER (marketing efficiency ratio, also called blended ROAS): total revenue ÷ total ad spend across every channel. The number for your monthly review, immune to attribution fights between platforms.

Break-even ROAS: the number where you start making money

Break-even ROAS is the ROAS at which an order covers its own ad cost. You calculate it from contribution margin.

A product sells for €79.90 gross, €67.14 net. Add cost of goods at €22.00, shipping at €4.50, payment fees at €1.60, and fulfillment at €3.00. Contribution margin per order: 67.14 − 22.00 − 4.50 − 1.60 − 3.00 = €36.04.

Break-even ROAS = 79.90 ÷ 36.04 = 2.2, calculated on gross revenue, the way your dashboard counts it.

As a reference, if you only know your margin:

• Contribution margin 20% of revenue: break-even 5.0
• 25%: break-even 4.0
• 30%: break-even 3.3
• 40%: break-even 2.5
• 50%: break-even 2.0

Anything below your break-even is paid reach, not a business. Returns lower your contribution margin and raise your break-even: if your return rate runs at 20%, build that into the contribution margin, not into a footnote.

Three ways your ROAS lies

• Attribution: the platform credits itself for view-through conversions and returning customers. A customer who would have bought anyway makes your ROAS look better, not your business. Look at new-customer ROAS separately. More on this: 5 reasons your tracking misleads you.
• Gross versus net: see the worked example above, plus your return rate. Dashboard ROAS knows nothing about VAT or returns.
• Channel silo: your Meta ROAS climbs while total revenue stays flat. The platform picked up conversions that belonged to Google or email, and MER exposes it.

What counts as a good ROAS?

A good ROAS sits above your break-even ROAS. There's no universal benchmark, because break-even depends on your margin.

An account with a 50% contribution margin turns a profit starting at 2.0. An account with a 25% margin still loses money at 3.5, because its break-even sits at 4.0. Industry benchmarks from blog posts are worthless unless they know your margin. If you can lower your ROAS and still earn more, because volume above break-even grows, you win. More on the cost side: Lower CAC without losing reach.

Run the numbers for your store

The Mesper profit calculator works out break-even and profit for your scenario: Open the profit calculator.

If you'd rather walk through it together: 15 minutes, no obligation. Book an intro call.

FAQ on ROAS

How do you calculate ROAS?

ROAS = revenue ÷ ad spend. Example: €12,000 in revenue from €3,000 in ad spend gives you a ROAS of 4.0.

What's the difference between ROAS and ROI?

ROAS sets revenue against ad spend, no other costs included. ROI sets profit against your total investment, including cost of goods, shipping, and fixed costs. A ROAS of 4.0 can correspond to an ROI of 26%, depending on your cost structure.

What counts as a good ROAS in ecommerce?

A good ROAS sits above that specific store's break-even ROAS. There's no fixed threshold, because margin determines break-even. At a high margin, a ROAS of 2.0 can be profitable. At a low margin, a ROAS of 4.0 can still mean a loss.

How high does ROAS need to be to turn a profit?

Break-even ROAS comes from gross revenue divided by contribution margin per order. At a €79.90 selling price and a €36.04 contribution margin, it lands at 2.2. Below that number, an order doesn't cover its own ad cost.

Run it with your own numbers

You do not have to work out the break-even by hand. The profit calculator gives you MER, break-even MER and monthly profit from your own figures.

Once that number stands and budget allocation is the real question, growth strategy is the place to start.