Analytics

How to Calculate Marketing Efficiency Ratio (MER)

MER divides total revenue by total marketing spend. Why it is the number platform attribution cannot inflate, and how to use it next to channel ROAS.

BenchMarketing editorial team Updated October 2, 2026 3 min read

Marketing efficiency ratio is the simplest honest measure of whether marketing is paying off. It ignores attribution entirely: total revenue divided by total marketing spend.

The formula

MER = total revenue ÷ total marketing spend over the same period.

$500,000 in revenue on $100,000 of marketing spend is an MER of 5.0. Some teams include only paid media in the denominator; others include agency fees, tools and content. Either is fine if you are consistent and say which you use.

Why MER matters

Every ad platform reports the revenue it can connect to its own ads. Customers see several channels before buying, so the platforms overlap, and the sum of platform-reported revenue is usually larger than what you actually earned. MER cannot double count, because it uses your real revenue.

MER versus ROAS

ROAS	MER
Revenue counted	What one platform attributes to its ads	All revenue
Spend counted	That platform's spend	All marketing spend
Good for	Optimising within a channel	Judging the whole marketing programme
Weakness	Overlaps with other channels	Cannot tell you which channel worked

Use both. ROAS tells you which campaigns inside a platform to scale; MER tells you whether scaling them grew the business.

Acquisition MER

Repeat customers buy whether or not you advertise to them. If most revenue comes from returning customers, MER can look healthy while acquisition fails. Calculate a second ratio using only first-order revenue from new customers. Watching it alongside MER shows whether you are buying growth or just being credited for loyal customers.

Setting a target

Your target MER follows from margin and fixed costs. Work backwards: what share of revenue can marketing take while leaving the profit you need? A business at 60% gross margin can run at a lower MER than one at 30%.

Reading changes

MER falls while spend rises: new spend is buying less than the old spend did. Normal up to a point; decide in advance how far you will let it fall.
MER rises after cutting a channel: that channel was probably taking credit for sales that happened anyway.
MER swings by season: compare with the same period last year rather than last month.

Compare yours on the MER benchmark page, or read our ROAS guide.

About the figures

Benchmark figures in this article come from the BenchMarketing dataset and update when the benchmark pages do. Each benchmark page lists its sources and period; see our methodology.

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