Mode
Ad A — control
Ad B — variant
Nothing is sent anywhere. Every calculation runs in your browser, and no figure you type leaves this page.
How to use this calculator
- Solve CTR when you have impressions and clicks and want the rate. The standard calculation.
- Solve clicks when you are forecasting: "at a 1.5% CTR, what does 200,000 impressions produce?"
- Solve impressions when you are working backwards from a click target.
- Compare two ads when you are about to pause a creative. Enter both, and the tool tells you how confident you can be that the difference is real.
Why the compare mode exists
Here is the mistake almost every ad account makes.
Two ads run for three days. One shows 1.9% CTR, the other 1.4%. The 1.9% one gets scaled and the other gets paused.
But if each ad only had 1,200 impressions, that gap is well inside the range you would expect from pure chance. Pause the "loser" and you may have just killed your better ad on a coin flip.
The compare mode runs a two-proportion significance test on your actual numbers and returns a confidence level. Above 95%, the difference is unlikely to be chance. Below 90%, you do not yet know anything and the test needs to keep running.
The formulas
| You want | Formula |
|---|---|
| CTR | (clicks ÷ impressions) × 100 |
| Clicks | impressions × (CTR ÷ 100) |
| Impressions | clicks ÷ (CTR ÷ 100) |
| Significance | two-proportion z-test on pooled standard error |
We have written the significance maths out in full in the comment at the top of this page's source, so anyone can check it rather than take our word for it. The full explanation of the metric itself is on our CTR guide.
Where CTR matters more than people think
- Quality Score. Expected click-through rate is one of the three components Google uses. A weak CTR raises what you pay for every click — see Quality Score.
- Ad Rank. CTR feeds the ad rank calculation, which decides whether you appear at all — see Ad Rank.
- Effective cost on CPM buys. When you pay per thousand impressions, CTR is what converts that price into a real cost per click. The CPM calculator does that conversion.
- Creative fatigue. A falling CTR on a stable audience is the earliest signal that the creative has been seen too often.
If your CTR is the problem rather than the measurement, start with ad copy and, on search, responsive search ads.
Why we do not publish a "good CTR"
Because the number is meaningless without its context.
A 2% click-through rate would be strong on display and poor on branded search. Position changes it, brand recognition changes it, placement changes it, and industry changes it. Any single benchmark is averaging across all of that.
Your own account history is the benchmark. And within a test, the other ad is the benchmark.
Frequently asked questions
How do you calculate CTR?
Divide clicks by impressions and multiply by 100 to get a percentage. An ad served 40,000 times that earned 520 clicks has a click-through rate of 1.3%. The same formula works for search ads, display ads, email and organic search results, though what counts as a good figure differs enormously between them.
How many impressions do I need before I can trust an A/B test?
There is no fixed number, because it depends on how large the difference is. A big gap between two ads becomes clear quickly; a small one may never separate. Rather than guessing, use the compare mode on this page — it runs a significance test on your actual numbers and tells you whether the gap you are seeing is bigger than the noise.
What does the confidence level actually mean?
It is the probability that a difference this large would not have appeared by chance if the two ads truly performed the same. At 95% confidence, there is roughly a one in twenty chance you are looking at random variation. Most teams treat 95% as the point where they act, but it is a convention rather than a rule.
Does a higher CTR always mean a better ad?
No, and this is the trap. An ad can win on click-through rate and lose on revenue, because a headline that promises more gets more clicks and disappoints more people. Click-through rate measures interest, not outcome. Always check conversion rate and cost per acquisition before you pause the loser.
What is a good CTR?
We are not going to publish a number. Click-through rate varies so much by platform, placement, ad position, brand recognition and industry that a single benchmark is meaningless — a 2% CTR could be excellent on display and poor on branded search. Compare against your own account history, and against the other ad in the same test.
We do not call a creative test on three days of data
Structured creative testing with a stopping rule agreed before the test starts.