ROAS, MER & POAS Calculator
This calculator computes three modern advertising efficiency metrics — Return on Ad Spend, Marketing Efficiency Ratio, and Profit on Ad Spend — from a single set of inputs so you can compare how your campaigns look under each framework. It is designed for performance marketers and e-commerce operators who have encountered the debate about which metric best reflects advertising health and want to see all three side by side rather than picking one arbitrarily. The tool makes it easy to explain the differences between platform-reported ROAS and business-level MER to finance and leadership teams.
Inputs
Results
How this is calculated
Enter your total ad spend, total attributed revenue, blended gross margin, and total business revenue, and the calculator produces ROAS, MER, and POAS simultaneously with brief explanations of what each figure indicates.
Every model runs locally in your browser. Nothing you type is sent anywhere.
Frequently asked questions
What is the difference between ROAS and MER?
ROAS, or Return on Ad Spend, is calculated using revenue attributed to advertising by ad platforms, which typically use last-click or view-through attribution. MER, or Marketing Efficiency Ratio, is calculated as total business revenue divided by total marketing spend with no attribution model — it is a blended, top-down measure of how much revenue the whole business generates per dollar of marketing investment. MER is harder to game and more stable than platform-reported ROAS, which is vulnerable to attribution window changes and cross-channel double-counting.
What is POAS and why is it better than ROAS for some businesses?
POAS, or Profit on Ad Spend, divides gross profit generated from ad-attributed sales by ad spend, rather than using revenue. This adjustment matters significantly for businesses with variable margins across products or customer segments, because a high ROAS on a low-margin product can actually destroy profit while appearing successful on a ROAS dashboard. POAS ensures that optimization is pointed at generating profit rather than revenue volume.
What MER should I target?
Target MER varies by business model and growth stage. A profitable steady-state e-commerce brand might target an MER of 4 to 6, meaning $4 to $6 in total revenue for every $1 of total marketing spend. A growth-stage business investing heavily in new customer acquisition may accept a lower MER of 2 to 3 while building its customer base. The most important thing is that your MER is calibrated against your unit economics so you know what level sustains profitability.