Reading CPM, CTR and CPA Together

Cost per acquisition feels like one number, but it's built from three: the price of attention (CPM), how often attention becomes a click (CTR) and how often a click becomes a conversion (CVR).

The identity

CPA = CPM ÷ (1000 × CTR × CVR). If CPA doubled, one of these changed. Find which one before touching anything.

• CPM up → auction pressure, narrow audience or seasonality.
• CTR down → creative fatigue or weak message–audience fit.
• CVR down → landing page, offer, price or tracking issues.

Why it matters

Teams often change targeting when the real problem is a broken checkout, or rewrite ads when the auction simply got expensive. Decomposition prevents fixing the wrong thing.

Try it with the CPA calculator in the tools section.