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A/B Test Calculator

Plan, run and analyze split tests with confidence. Statistical significance, sample size and test duration — all in one free, browser-based tool.

Test data

Enter visitors and conversions for each variant. Variant A is the control. You can add up to 5 variants.

Test settings

How many visitors per month will see the page after you roll out the winner.

Results

Verdict
Add data to see results
Enter visitors and conversions for at least two variants to calculate statistical significance.
Best variant
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Observed lift
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P-value (frequentist)
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Probability winner is better (Bayesian)
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Beta(1,1) prior, normal approximation

Test parameters

Plan how many visitors per variant you need before starting your test.

Your current conversion rate for the variant you want to beat.
Smallest relative lift you want to detect. A 10% lift on a 3% baseline means detecting a 3.3% conversion rate.

Sample size needed

Visitors needed per variant
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Total visitors needed
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Conversions per variant
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Detecting
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Absolute lift to detect
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Traffic & expectations

Estimate how many days you need to run your test based on your current traffic.

Total daily visitors that will be split across variants.

How long to run the test

Estimated duration
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Days needed
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Weeks needed
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Visitors per variant
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Total visitors
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Recommendation: Run your test for full weekly cycles (multiples of 7 days) to capture weekday/weekend variation. Avoid stopping the test early or peeking at results before reaching the calculated sample size.
Tools that work well together
📡 UTM BuilderTag your test variants in analytics 💸 Price WizardTest pricing scenarios with confidence 🔎 Meta Tag PreviewTest SERP titles and descriptions

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