MER Calculator Widget
Embed a marketing efficiency ratio calculator for ecommerce and DTC readers. It divides total revenue by total marketing spend, shows new-customer MER (aMER) when new-customer revenue is known, and turns a target MER into the most you can spend on a revenue plan.
Live preview
Under the widget on your page: Powered by A2Z Tools
Embed code
<iframe src="https://a2z.tools/embed/w/mer-calculator" title="MER Calculator by A2Z Tools" width="100%" height="640" style="border:0;width:100%" loading="lazy" allow="clipboard-write"></iframe>
A plain iframe. Works everywhere, including site builders that strip scripts. Adjust height if your content needs more room.
<div data-a2z-widget="mer-calculator" data-height="640"></div> <script async src="https://a2z.tools/embed.js"></script>
Adds a small script (what it does) that sizes the widget to fit its content, loads it lazily and keeps it isolated from your page's CSS.
Works with
How it works
MER, sometimes called blended ROAS, uses only two totals from the business's own books: all revenue in a period and all marketing spend in it, including every ad platform, agency fees and creator payments. 500,000 of revenue on 100,000 of spend is an MER of 5.0, which also means marketing takes 20% of revenue. Platform ROAS, by contrast, is each ad network's claimed revenue divided by its own spend; because platforms attribute overlapping sales, platform ROAS figures usually add up to more than the business actually earned. New-customer MER (aMER, also called ncROAS) divides revenue from first-time buyers by the same total spend - 200,000 gives 2.0 - which shows how efficiently marketing buys growth rather than repeat sales. With a target MER the widget divides a revenue plan by it to give a spend ceiling and compares it with current spend.
Calculation method
- MER = total revenue / total marketing spend
- Marketing share of revenue % = spend / revenue x 100 (= 100 / MER)
- aMER (ncROAS) = new-customer revenue / total marketing spend
- Max spend = revenue plan (or current revenue) / target MER; headroom = max spend - current spend
Worked examples
Planning next quarter
Inputs: Revenue 500,000; spend 100,000; new-customer revenue 200,000; target MER 4; plan 600,000
Result: MER 5.00x; marketing 20% of revenue; aMER 2.00x; max spend 150,000; headroom 50,000
600,000 / 4.
Over budget
Inputs: Revenue 300,000; spend 120,000; target MER 3
Result: MER 2.50x; marketing 40% of revenue; max spend 100,000; over budget by 20,000
Ceiling based on current revenue when no plan is given.
Limitations
- MER shows overall efficiency, not which channel works; it cannot replace incrementality tests or channel attribution.
- Revenue and spend must cover the same period; long sales cycles and subscriptions blur the ratio.
Where publishers use it
- DTC and Shopify growth blogs explaining blended performance metrics
- Performance-marketing agencies reporting beyond in-platform ROAS
- Founder and CFO newsletters setting next quarter's marketing budget
- Ecommerce analytics tool pages comparing attribution approaches
- Marketing courses teaching the gap between platform and business numbers
- Investors and lenders comparing marketing efficiency across ecommerce portfolio companies
Questions
How is MER different from ROAS?
ROAS divides the revenue an ad platform attributes to itself by that platform's spend. MER divides all revenue by all marketing spend, so it cannot double-count sales two platforms both claim.
What is a good MER?
It depends on gross margin. A business with a 60% gross margin breaks even on marketing at an MER of about 1.67 (1 / 0.6); with 40% margin it needs 2.5 just to cover the ads.
What is aMER or ncROAS?
New-customer revenue divided by total marketing spend. 200,000 from first-time buyers on 100,000 of spend is 2.0, showing how much growth each unit of spend buys.
What should count as marketing spend?
Every paid channel plus agency retainers, creator and affiliate payouts, and promotional discounts if you treat them as marketing. Leave out salaries only if you do so every period.
How does the spend ceiling work?
At a target MER of 4 and a revenue plan of 600,000, spend can reach 150,000. At 300,000 revenue and an MER target of 3, the ceiling is 100,000, so spending 120,000 is 20,000 over.
Why does MER look worse than the dashboards?
Meta, Google and TikTok each use their own attribution windows and view-through credit, so one purchase can be claimed by several dashboards. Summed platform ROAS of 7x can sit beside a business MER of 4x.
How is MER used for budgeting?
Finance teams set a floor such as 3x, forecast revenue by month and let the spend ceiling flex with it - so a seasonal peak month can carry far more spend than a quiet one while the blended efficiency stays on target.
Cite or recommend this tool
If you reference this tool in an article, course or documentation, these formats are ready to copy. They are optional - nothing is added to your site unless you paste it.
A2Z Tools MER Calculator https://a2z.tools/embed/mer-calculator
<a href="https://a2z.tools/embed/mer-calculator">A2Z Tools MER Calculator</a>
[A2Z Tools MER Calculator](https://a2z.tools/embed/mer-calculator)
MER Calculator by A2Z Tools - https://a2z.tools/embed/mer-calculator
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