A/B Test Calculator
Check whether your A/B test result is statistically significant.
Enter your values to see the result.
Uses a two-tailed two-proportion z-test. Decide your sample size before the test starts and do not stop the moment it turns significant, or false wins become likely.
Continue your work
- Percentage Calculator — Work out percentage changes.
- UTM Link Builder — Tag the traffic sent to each version.
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Clear instructions
Find steps, examples and limitations below.
Use online
Open the tool in a supported web browser.
Free to use
No sign-up required. Tool-specific limits may apply.
How to use the A/B Test Calculator
Check whether your A/B test result is statistically significant.
- 1 Enter visitors and conversions for version A (control) and version B.
- 2 Choose the confidence level you require, usually 95%.
- 3 Read whether the difference is significant and the uplift.
Example and practical tips
5,000 visitors per version with 250 and 300 conversions is a 20% uplift with 97% confidence, which is significant at 95%.
Frequently asked questions
What is statistical significance?
It means the difference is unlikely to be random chance at the chosen confidence level.
Can I stop the test as soon as it is significant?
No. Decide the sample size in advance; checking repeatedly and stopping early greatly increases false winners.
Report an issue
Something broken or not quite right? Tell us and we will look into it.