What is MER? Marketing efficiency ratio explained
MER, or marketing efficiency ratio, divides all your revenue by all your marketing spend. Here is what MER means, how to calculate it, a worked example, why it differs from platform ROAS and how to use the two together.
MER, or marketing efficiency ratio, is your total revenue divided by your total marketing spend over the same period. It ignores which channel claims each sale, so ad platforms double counting cannot inflate it. Many ecommerce teams call it blended ROAS and use it as a top-line check on the numbers each platform reports.
How do you calculate MER?
| Metric | Formula |
|---|---|
| MER | Total revenue ÷ total marketing spend |
| Marketing cost ratio (the inverse) | Total marketing spend ÷ total revenue |
Decide what goes into the spend line and keep it fixed: most teams include all paid media, and some add agency fees, influencers and tools. Use revenue net of VAT, and decide whether returns and refused cash-on-delivery orders come out.
MER example
An illustrative month for a Saudi fashion brand:
- Total net revenue from all channels, including organic and repeat customers: SAR 900,000.
- Total marketing spend across Snapchat, TikTok, Meta, Google and influencers: SAR 200,000.
- MER = SAR 900,000 ÷ SAR 200,000 = 4.5.
Meanwhile the ad platforms together claim SAR 1,100,000 of revenue, more than the business actually made. MER is designed to ignore that gap.
What is a good MER?
It depends on your margin and on how much revenue comes from repeat customers and organic channels, which MER counts even though ads may not have driven it. Compare MER with your own history and with the ratio your margin supports: if 40% of revenue is left after variable costs, MER must stay above 2.5 for marketing to pay for itself. The ROAS calculator works on blended figures too.
MER vs ROAS
ROAS uses the revenue each platform attributes to its own ads, so it tells you which campaigns to adjust. MER uses all revenue and all spend, so it tells you whether marketing as a whole is paying off. When they disagree sharply, check your attribution model and test with incrementality holdouts. Our guide to attribution models explains why platforms over-claim.
How Grower helps
Grower compares your budgets against live spend from connected channels and generates budget insights every month. Its attribution engine de-duplicates conversions from every channel and app into one unified conversion count.
Frequently asked questions
Is MER the same as blended ROAS?
Mostly, yes. Both divide total revenue by total spend without channel attribution. Some teams use blended ROAS for paid media only and MER for all marketing costs, including agencies, influencers and tools. The name matters less than writing down what goes into each side and keeping it the same from month to month.
Why is my MER lower than my platform ROAS?
Usually because several ad platforms claim the same sales. Meta, Google, TikTok and Snapchat each credit conversions inside their own windows, some including ad views, and none de-duplicates against the others. Adding their attributed revenue overstates the total, while MER only counts the revenue the business actually booked.
Should I optimize for MER or ROAS?
Use both, for different decisions. Platform bidding needs ROAS or CPA signals, so leave those inside each channel. Set your overall budget against a MER target derived from your margin, then shift spend between channels using a de-duplicated attribution view. If MER falls while platform ROAS holds steady, the platforms are probably over-claiming.
Check your blended number with the free ROAS calculator, or book a demo to see spend and conversions from every channel in one place.