A/B Test Significance Calculator
Is your test result real?
Enter your values
ⓘ Live results
Results
- Significant?
- Yes at 95% confidence
- Control rate
- 6%
- Variant rate
- 7.2%
- Relative lift
- 20.1%
Quick answer
A test is significant when the observed difference is unlikely to have happened by chance.
z = (p1 − p2) ÷ √(p(1−p)(1/n1 + 1/n2))
How to use the A/B Test Significance Calculator
- 1Enter visitors and conversions for the control.
- 2Enter the same for the variant.
- 3Only stop the test once it reaches significance.
Worked example
Using the values the calculator loads with:
Inputs
- Control visitors5200
- Control conversions312
- Variant visitors5150
- Variant conversions371
Results
- Significant?Yes at 95% confidence
- Control rate6%
- Variant rate7.2%
- Relative lift20.1%
Frequently asked questions
Can I peek early?
Peeking inflates false positives — set a sample size before you start.
What if lift is big but not significant?
Keep running; small samples produce large, unreliable swings.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.