ROAS vs MER vs POAS: which number to run a Shopify store on
What ROAS, MER, POAS and break-even ROAS measure, how to calculate each one, and when each is the right number for a Shopify store.
Short answer: ROAS is revenue a platform credits to its ads divided by what you spent there. MER is all store revenue divided by all ad spend, so it does not depend on any platform's attribution. POAS replaces revenue with profit. Use ROAS to compare campaigns inside a platform, MER to check the whole business, and POAS when product margins differ.
The formulas
| Metric | Formula | Answers |
|---|---|---|
| ROAS | Attributed revenue ÷ ad spend | Which campaign, ad set or ad returns most per dollar |
| MER (blended ROAS) | Total revenue ÷ total ad spend | Is advertising as a whole paying off |
| POAS | Profit ÷ ad spend | Which ads make money after costs |
| Break-even ROAS | 1 ÷ gross margin | The lowest ROAS that does not lose money |
| CPA | Ad spend ÷ orders | What each order costs to acquire |
A worked example
Illustrative numbers. A store spends $10,000 on ads in a month and sells $40,000 in total. Meta credits itself with $30,000.
- Meta ROAS: 30,000 ÷ 10,000 = 3.0
- MER: 40,000 ÷ 10,000 = 4.0
- With a 40% gross margin, break-even ROAS is 1 ÷ 0.4 = 2.5, so both are above it.
- If profit after product costs, fees, shipping and ads is $3,000, POAS is 3,000 ÷ 10,000 = 0.3.
Where each one misleads
- ROAS depends on the platform's attribution window and model, and platforms can credit the same order.
- MER includes organic and repeat sales, so it can look healthy while new campaigns lose money.
- POAS is only as good as the cost data behind it: product costs, payment fees and shipping.
How TRACK ATLAS reports them
The TRACK ATLAS Summary shows ROAS as total sales divided by ad spend across connected platforms, MER as ad spend divided by total sales in percent, CPA, POAS as net profit divided by ad spend, and net profit and margin after product costs from Shopify, payment fees, shipping, handling and other costs. Platform-reported ROAS sits next to them for each ad platform.
Questions
What is a good ROAS?
One above your break-even ROAS, which is 1 divided by your gross margin. A store with a 40% margin breaks even at a ROAS of 2.5.
Is MER the same as blended ROAS?
Yes, when it is written as total revenue divided by total ad spend. Some tools show it the other way round, as spend divided by revenue in percent, so check which one a report uses.
Why use POAS?
Two campaigns with the same ROAS can earn very different profit if they sell products with different margins. POAS uses profit, so it shows which one actually pays.
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