Run
A/B Test Duration Calculator
Find out exactly how many days to run your A/B test for statistically valid results.
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Free CRO tools
Professional-grade calculators for A/B testers, CRO specialists, and growth teams. Calculate test duration, sample sizes, and statistical significance, all free, no signup required.
All free CRO tools
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Size
Sample Size Calculator
Calculate the minimum visitors per variation needed to detect a meaningful difference.
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Evaluate
Statistical Significance Calculator
See whether your A/B test reached significance, with p-value and observed lift.
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Plan
Test Velocity Calculator
Plan your testing roadmap: how many valid experiments your traffic supports.
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Want a full CRO audit?
These tools help you run better tests, but they can't tell you what to test. A free audit scores your page and ranks the findings by impact.
Why it matters
Why CRO math matters
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Avoid false positives
Ending a test early because results "look good" is one of the most common and costly CRO mistakes. Using proper sample sizes ensures your results are real, not just random noise.
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Ship winning changes
Statistical significance tells you whether a difference is likely real or coincidental. Without it, you might ship changes that actively hurt conversions.
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Plan tests properly
Knowing your required sample size before you start lets you plan test duration realistically, allocate traffic correctly, and avoid wasting weeks on underpowered experiments.
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Credible reporting
Share p-values and confidence levels with stakeholders to build trust in your CRO program. Data-driven decisions require data-driven evidence.