Metrics & KPIs

MER vs POAS

In short: Both push back against relying on platform-reported ROAS alone, but they fix different blind spots. MER strips out attribution altogether and looks at total company revenue against total marketing spend, trading precision for a number that survives tracking breakage and covers every channel at once. POAS keeps attribution at the campaign or product level but replaces the revenue numerator with gross profit, exposing that cheap high-margin items and pricey low-margin ones can look identical on ROAS while contributing very differently to the business. If your problem is that you don't trust attribution, reach for MER; if your problem is that ROAS treats every SKU the same, reach for POAS.

By the AdFlint research team · Fact-checked against current Google and Meta platform behavior · Last reviewed July 2026

MER

Total company revenue divided by total marketing spend across all channels, a blended efficiency ratio rather than any per-campaign measurement.

It sidesteps attribution entirely by refusing to assign credit, asking only what every marketing dollar coincided with in revenue. That makes it stable when tracking degrades, but blunt: it also moves with organic demand, email, retention, and seasonality. The common misreading is diagnosing a single channel from it, which by construction it cannot tell you anything about.

Full definition

POAS

Gross profit attributed to advertising divided by ad spend, replacing the revenue numerator in ROAS with revenue minus cost of goods.

It exposes what revenue reporting hides: a catalog where cheap high-margin items and expensive low-margin ones look identical on ROAS but differ completely in contribution. Feeding margin into bidding usually shifts delivery toward better products. The main pitfall is a stale or incomplete margin feed, which produces confident optimization toward numbers that no longer reflect actual product costs.

Full definition

Side by side.

The differences that actually change what happens in your account.

	MER	POAS
What the numerator is	Total company revenue across every channel, including organic and offline.	Gross profit attributed to advertising - revenue minus cost of goods.
What the denominator is	Total marketing spend across every channel.	Ad spend on the specific campaign, product, or channel being measured.
Attribution dependency	None - it deliberately refuses to assign credit to any channel.	Full - it needs the same conversion attribution ROAS uses, plus a working margin figure per item.
What it's good at diagnosing	Whether overall marketing spend is efficient at the company level, especially when tracking is degraded.	Whether a specific campaign or product is actually contributing profit, not just revenue.
What it can't diagnose	Which channel, campaign, or product is responsible for a change - by design it can't be decomposed.	Company-wide efficiency across channels it doesn't have data for, or spend outside advertising entirely.
Sensitivity to	Everything happening in the business at once - organic demand, email, retention, seasonality - not just paid media.	The accuracy and freshness of the margin feed behind each product.
Failure mode	Using it to diagnose a single channel's performance, which it structurally cannot do.	A stale or incomplete cost-of-goods feed, which produces confident-looking optimization toward numbers that no longer reflect real costs.

What actually separates them.

MER ignores which channel gets credit for a sale; POAS depends entirely on attribution working correctly at the campaign or product level.

MER uses revenue in the numerator like ROAS does; POAS replaces that revenue with gross profit, so the two aren't measuring the same kind of return even when both are expressed as a ratio.

MER moves with things advertising didn't cause - organic search, email, word of mouth - while POAS only reflects what a specific ad campaign or product actually did.

You can feed POAS into automated bidding as a value signal per product; MER has no per-product resolution to feed anywhere - it's a reporting metric, not a bidding input.

A broken pixel or consent-driven tracking loss degrades POAS accuracy immediately, while MER is largely immune to that specific failure since it doesn't rely on per-click attribution at all.

Which one should you use?

Use MER when

iOS privacy changes or consent banners have made your platform-reported attribution unreliable and you need a number that doesn't depend on it.
You want a single sanity check on total marketing efficiency without breaking it down by channel.
You're presenting to ownership or finance who care about total marketing spend against total company revenue, not campaign-level detail.
You run a mix of paid, organic, email, and offline and want a metric that captures the combined effect of all of them.

Use POAS when

You sell a catalog where products have meaningfully different margins and ROAS is treating a low-margin item the same as a high-margin one.
You want to feed real product-level value into automated bidding so the algorithm favors your more profitable items.
Your attribution is solid enough at the campaign level to trust a per-product profit calculation.
You need to justify a specific campaign or product line's contribution to the business, not overall marketing health.
You're deciding which SKUs to push harder in ads and which to pull back, and revenue alone is giving you the wrong answer.

Common questions.

Should I use MER or POAS to judge a single campaign?

POAS, since it's attributed to that specific campaign and reflects the actual margin of what it sold. MER can't be broken down to a single campaign by design - use it for whole-account or whole-business health instead.

Why is my MER healthy but individual campaign ROAS numbers look weak?

MER captures revenue from every source - organic search, email, direct traffic, retention - not just the paid campaigns you're looking at. It's common for MER to look fine while specific paid channels underperform, because other parts of the business are carrying the total.

Can I calculate POAS without a full margin feed?

You can approximate it with a blended average margin across your catalog, but that reintroduces the exact distortion POAS exists to fix - it will treat high and low margin products the same again. A real per-SKU or per-category cost feed is what makes POAS worth calculating over plain ROAS.

Does a rising MER mean my ads are working better?

Not necessarily. Because MER includes every revenue source against every marketing dollar, a rising number can come from stronger organic demand, a seasonal spike, or better retention just as easily as from better ad performance. Check channel-level and product-level metrics like POAS before crediting the ads.

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