# ROAS vs MER

> ROAS measures one platform's return. MER measures the whole business. When each one misleads, how to use both, and a worked example.
- **Author**: Marxx
- **Published**: 2026-10-26
- **Category**: Metrics
- **URL**: https://marxx.ai/library-compare/roas-vs-mer

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ROAS tells you which campaign or platform to back, using revenue the ad platform reports. MER tells you if all your marketing together pays, using real revenue from your store. Use MER to set the budget and ROAS to split it.

## Side by side

| | ROAS | MER |
|---|---|---|
| Formula | Platform revenue / platform spend | Total revenue / total marketing spend |
| Revenue from | Meta, Google, etc. | Your store or accounts |
| Scope | One campaign or channel | The whole business |
| Double counting | Possible across platforms | Not possible |
| Answers | Which ad or channel works best? | Is our marketing paying overall? |

## A worked example

October results:

- Meta: INR 3,00,000 spend, reports INR 12,00,000 revenue. ROAS 4.0.
- Google: INR 1,00,000 spend, reports INR 5,00,000. ROAS 5.0.
- Store total revenue: INR 13,00,000.

Platforms claim INR 17,00,000. The store sold INR 13,00,000. Counting only ad spend, MER = 13,00,000 / 4,00,000 = **3.25**.

Both ROAS figures look healthy, but the real return is 3.25. If your break-even is 3.0, you have little room to scale.

## When each misleads

- **ROAS** inflates when platforms share credit for the same buyer, or when retargeting takes credit for buyers who would have bought anyway.
- **MER** moves with things that are not ads: a sale, a viral post, a price change.

## How to use both

1. Set a MER target from your margins. That caps total spend.
2. Within that, move budget to campaigns with better ROAS.
3. Check with an [incrementality](/glossary/incrementality) test once or twice a year.

## FAQ

### Is blended ROAS the same as MER?

Nearly. Blended ROAS is total revenue divided by total ad spend. MER uses the same revenue but some teams divide by all marketing cost, such as agency fees and tools. If you count only ads, the two match.

### Should I include organic revenue in MER?

Yes. MER uses total revenue, so organic sales count. That is also why MER can rise without any change in ads.

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