Guide · 4 min read
CPC vs CPM vs CPA — three ad costs, one simple example.
They all start with "cost per", they all appear in your ads dashboard, and they measure completely different things. Here's the whole story with one campaign.
One campaign, three lenses
Say you spend $100. Your ad is seen 20,000 times, gets 400 clicks, and 10 people buy.
| Metric | Formula | Our example | It tells you the price of… |
|---|---|---|---|
| CPM cost per 1,000 impressions | spend ÷ impressions × 1000 | $5.00 | …being seen |
| CPC cost per click | spend ÷ clicks | $0.25 | …a visit |
| CPA cost per acquisition | spend ÷ conversions | $10.00 | …a customer |
Same $100 — three different stories. And notice how they chain together: cheap impressions mean nothing if nobody clicks, and cheap clicks mean nothing if nobody buys.
Which one should you watch?
- Building awareness (new brand, just want eyeballs) → watch CPM. You're buying attention; pay less per thousand.
- Driving traffic (blog, launch page, offer) → watch CPC. You're buying visits.
- Selling something → watch CPA, always. The only question that matters: does a customer cost less than they're worth?
The golden rule: your CPA must stay below the profit one
customer brings you. If a sale earns you $15 profit and a customer costs $10 of ads to
acquire, you have a money machine. If it costs $20, you have an expensive hobby.
Common beginner mistakes
- Optimizing CPC when you sell things. The cheapest clicks often come from the least serious visitors. A $0.10 click that never buys is worth less than a $1 click that does.
- Comparing CPM across different audiences. Reaching CEOs costs more per thousand than reaching students — a higher CPM isn't automatically "worse".
- Judging CPA with too little data. Ten clicks and no sales doesn't mean CPA is infinite — it means you don't have enough data yet. Give campaigns a few hundred clicks before judging.
See all three at once
Our free calculator takes the five numbers from your ads dashboard and returns CPM, CPC, CPA, CTR, conversion rate and ROAS together — so the whole chain is visible.
Open the ad metrics calculator