Read CPM, CTR and CPA together
None of these three metrics means much alone. Read together, they show you exactly what to fix.
Three different questions
CPM (cost per 1,000 impressions) answers: how much does it cost to reach this audience? It tells you about the market and competition, not your ad.
CTR (click-through rate) answers: does my hook make people want more? It tells you about the creative and how well it fits the audience.
CPA (cost per purchase, or cost per lead for leads) answers: is this making money? It’s the only one about money, and it’s the one that decides.
Read them as a chain
When your CPA gets worse, work back up the chain. Did CPM go up? Then the problem is upstream: a busy season, an audience that’s too narrow, or more competition in your niche. Did CTR drop? Then it’s creative: the ad is tired, or it doesn’t speak to this audience.
If CPM and CTR are steady but CPA climbs, the problem is after the click: landing page, price, stock, or checkout. The ad is doing its job. What comes next isn’t.
The low-CPM trap
A low CPM looks like good news. It only is if the rest follows. A broader audience or cheaper placements will lower CPM on their own. If those impressions don’t convert, you just bought cheaper attention that’s just as useless.
Same with CTR. A hook that teases without saying what you sell gets lots of clicks and no buyers.
How long to look
Never just one day. Daily volume is too low for a swing to mean anything, and you’ll end up reacting to noise. A rolling 7 days works for most accounts. Then compare it to the previous period of the same length.
That’s exactly what Adwize does when you ask why your cost moved. It compares two matching periods, works up the chain, and tells you where the problem is before it suggests anything.