Ecommerce

MER Calculator

Marketing efficiency ratio divides all revenue by all marketing spend, which is the number platform ROAS cannot inflate.

Everything you earned against everything you spent

The whole business, for one period

All revenue in the period, in your local currency.

All marketing costs across every channel.

MER (marketing efficiency ratio)

4.00

Total revenue per unit of total marketing spend.

Formula verified 13 September 2026

Marketing as % of revenue

25.00%

Share of revenue spent on marketing.

Revenue per marketing unit

4.00

Revenue earned per unit of marketing spend.

Report an issue

Estimate only — platform fees and costs vary; verify current rates. Read the full disclaimer ↓

MER efficiency bands

Where your computed MER falls as a rough efficiency read. Because MER blends organic and repeat revenue, a "good" level depends heavily on margin and revenue mix — judge it against your own break-even economics and trend, not a universal benchmark.

RangeWhat it typically suggests
Below 2.0Marketing absorbs a large share of revenue — sustainable only on high margins; thin-margin brands likely lose money here.
2.0 – 4.0A common operating range; efficiency is moderate, and profitability hinges on margin and how much revenue is organic.
4.0 – 6.0Efficient blended performance — revenue comfortably outpaces total marketing spend for most margin profiles.◀ your MER (4.00x)
Above 6.0Very efficient, but may signal under-investment in growth, or simply a large organic base inflating the ratio.

Estimates only — not financial, tax, or professional advice.

100% private — every number you enter is calculated in your browser and never sent to our servers.

What it calculates: MER (marketing efficiency ratio), Marketing as % of revenue, Revenue per marketing unit.

Updated 5 June 2026 · Transparent assumptions

Every channel claims the same sale, and MER cannot

Each ad platform reports conversions it believes it caused, using its own attribution window and its own view. Run three channels and the credited revenue frequently exceeds the revenue the business actually booked, because the same order is claimed more than once.

MER sidesteps attribution completely: total revenue over total spend. It cannot tell you which channel worked, but it cannot be gamed by any of them either, which is why it is the figure to steer the budget by.

The break-even MER is one divided by your contribution margin

An MER of 4 means four units of revenue per unit of marketing spend, or 25% of revenue going to marketing. Whether that is sustainable depends entirely on gross margin: a business at 30% contribution margin cannot afford an MER of 4, while one at 70% comfortably can.

Break-even MER is the reciprocal of contribution margin. At 50% margin, break-even is 2; anything above that contributes to fixed costs and profit, anything below it loses money on every additional order.

That is a feature, and it is also the main objection

MER includes revenue that no advertisement caused — direct traffic, organic search, returning customers, email to an owned list. A brand with strong organic demand will show a flattering MER even with mediocre advertising.

That is the honest criticism of the metric, and the standard answer is to watch MER alongside the share of revenue that is genuinely new-customer revenue. A rising MER driven entirely by returning customers is a different business result from one driven by efficient acquisition.

Agency fees, tools and creative belong in spend

Counting only media spend and excluding agency retainers, software subscriptions, influencer fees and creative production understates the true cost and makes the ratio look better than the business is performing.

Whichever definition you choose, hold it constant. A ratio that improves because a cost moved out of the denominator is the most common way this metric misleads the people relying on it.

Sources & References

Figures on this page are checked against primary, authoritative sources. Links open in a new tab.

Related Calculators

Blended ROASOne return on ad spend across every channel, so the same order is never credited twice.
Ad SpendThe budget a revenue target needs at your ROAS, or the revenue a budget should return — solved either way.
Break-Even ROASWork out break-even and target ROAS from your real margins, plus max CAC, break-even MER, and ad budgets.
LTV:CACCalculate CAC, discounted LTV, the LTV:CAC ratio, and CAC payback, with channel-by-channel decisions and scenarios.

More in Business, or browse all calculators.

Business disclaimer

Results are estimates for planning and analysis based on the figures you enter. They are not accounting, tax, or financial advice — verify with your own records and a qualified professional before making decisions.

How we calculate · Found an error? email us

Authorship & verification

Written and maintained by , a business operator who builds spreadsheet-based calculators.

What's changed (3 updates)

Published 13 September 2026

  1. Published the calculator with its formula, worked example, assumptions, limitations and a bespoke guide, and added an automated formula test suite covering it.
  2. Tested the marketing efficiency ratio as revenue over spend, with marketing as a share of revenue as its reciprocal.
  3. Tested that the ratio and the percentage are exact reciprocals of each other at every level of spend.

Add this calculator to your site

Responsive embed — and private: nothing your visitors type leaves their browser.