Advertising numbers are easy to mix up. A cheap CPM sounds good until nobody clicks, and a great click-through rate means little if no one buys. These free calculators show the formula behind each result, walk through worked examples, and explain what the number means for your campaigns, so you can check the math instead of just trusting it.
Calculators
- CPM Calculator: find your cost per 1,000 impressions, plan an ad budget, or see how many impressions a budget buys. It can also follow the result through to cost per click and cost per acquisition.
How do the main ad metrics connect?
Every campaign runs along the same chain. You pay for impressions, some people click, some of those clicks convert, and the conversions bring in revenue. Each step has its own metric.
| Metric | What it tells you | Formula |
|---|---|---|
| CPM | What 1,000 impressions cost? | (cost ÷ impressions) × 1,000 |
| CTR (click-through rate) | How many impressions turn into clicks? | clicks ÷ impressions × 100 |
| CPC (cost per click) | What each click costs? | cost ÷ clicks |
| Conversion rate | How many clicks turn into customers or leads? | conversions ÷ clicks × 100 |
| CPA (cost per acquisition) | What each conversion costs? | cost ÷ conversions |
| ROAS (return on ad spend) | Revenue earned per dollar of ad spend | revenue ÷ ad spend |
| CAC (customer acquisition cost) | What it costs to win one new customer? | sales and marketing cost ÷ new customers |
A worked example
You spend $1,000 and get 100,000 impressions, so your CPM is $10. A 1% CTR gives 1,000 clicks, which makes your CPC $1.00. A 3% conversion rate gives 30 customers, so your CPA is $33.33. If each customer spends $80, you earn $2,400, and your ROAS is 2.4.
Is that good? It depends on your margin. Break-even ROAS is 1 divided by your profit margin. With a 40% margin, break-even is 2.5, so a ROAS of 2.4 loses about $40 on this campaign even though it looks healthy. That’s why the numbers are worth following through the whole chain, not judging one in isolation.
Which metric answers which question?
- “What does reach cost me?” Look at CPM.
- “Is my ad interesting enough to click?” Look at CTR.
- “What does a visit cost?” Look at CPC.
- “What does a customer cost?” Look at CPA and CAC.
- “Am I making money?” Look at ROAS, against your break-even ROAS.
Common mistakes with ad metrics
- Judging a campaign by a single number, such as a low CPM, without checking what follows it.
- Comparing platforms without comparing click-through and conversion rates.
- Forgetting margin, so a healthy-looking ROAS still loses money.
- Mixing date ranges or currencies across reports.
How do I keep these calculators accurate?
Every calculator is tested against examples I’ve worked out by hand, and benchmarks come from named sources with the date I checked them. You can read more on the How We Calculate page.