Google Ads Health

PMax vs Search Cannibalisation Estimator

How much of your Performance Max volume is really brand or existing Search traffic, not genuinely new demand?

How to use

Enter your before/after numbers

Search conversions before PMax launched, and Search + PMax conversions now.

Estimate the brand share

Roughly what share of PMax spend you believe is brand/existing-customer traffic.

See the incrementality estimate

A rough read on how much of PMax's reported total is genuinely new versus reshuffled.

Search-only conversions/month BEFORE PMax launched

Search conversions/month NOW (with PMax also running)

PMax conversions/month

Estimated brand/existing-customer share of PMax (%) your best guess — check Search terms insights

Estimate

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Search conversions lost since PMax launched

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Estimated brand conversions inside PMax

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Estimated genuinely incremental conversions

A directional estimate from numbers you provide, not a Google-verified incrementality test. For a rigorous answer, run a proper geo or conversion-lift experiment.

How it calculates

Search conversions lost = Search-only conversions before PMax launched, minus Search conversions now (with PMax also running).
Estimated brand conversions inside PMax = current PMax conversions × your estimated brand/existing-customer share (check Search terms insights for a realistic figure).
Estimated genuinely incremental conversions = (Search now + PMax now) − Search-only before — the growth PMax can actually claim once the conversions it likely just reshuffled from Search are accounted for.
A directional estimate from numbers you provide, not a Google-verified incrementality test — for a rigorous answer, run a proper geo or conversion-lift experiment.

Related tools

Auction Insights Visualiser — See whether your Search auction share dropped at the same time PMax launched
Seasonality vs Trend Separator — Rule out ordinary week-to-week noise before blaming PMax for a Search dip
Recommendation Second Opinion — Read the honest verdict on “upgrade to Performance Max” before or after running this estimate

Last updated: 19 August 2026 · Built by the CWA Europe PPC team.

Frequently asked questions

Is this a Google-verified incrementality test?

No — it is a directional estimate from numbers you provide. For a rigorous answer, run a proper geo-holdout or conversion-lift experiment.