A/B Test Significance Calculator
Is your test result real?
Enter your values
Enter the control visitors you are working with.
Enter the control conversions you are working with.
Enter the variant visitors you are working with.
Enter the variant conversions you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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))
At a glance
| What it does | Is your test result real? |
|---|---|
| Category | Business |
| Inputs needed | Control visitors, Control conversions, Variant visitors, Variant conversions |
| Main output | Significant? |
| Formula | z = (p1 − p2) ÷ √(p(1−p)(1/n1 + 1/n2)) |
| Cost | Free — no sign-up, no download |
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.
Inputs explained
- Control visitors
- Enter the control visitors you are working with.
- Control conversions
- Enter the control conversions you are working with.
- Variant visitors
- Enter the variant visitors you are working with.
- Variant conversions
- Enter the variant conversions you are working with.
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.
What do I need to enter into the A/B Test Significance Calculator?
Just 4 values: control visitors, control conversions, variant visitors, variant conversions. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the A/B Test Significance Calculator work out the answer?
A test is significant when the observed difference is unlikely to have happened by chance. It applies the formula z = (p1 − p2) ÷ √(p(1−p)(1/n1 + 1/n2)) and shows the working so you can check each step by hand.
Is the A/B Test Significance Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.