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A/B Test Duration Calculator

Find out exactly how long your A/B test needs to run before results are trustworthy. Enter your daily traffic and conversion goals — avoid calling tests too early or wasting time running them too long.

Estimated Test Duration

Enter your parameters and click Calculate to see the estimated duration

Understanding Test Duration

Sample Size Calculation: The calculator uses an industry-standard formula that accounts for both your baseline conversion rate and the minimum effect you want to detect.

Daily Traffic Split: The calculator assumes an equal 50/50 split of your daily traffic between the control and test variations.

Confidence Level: A higher confidence level (e.g., 99% vs. 95%) increases the required sample size. Industry standard is 95%.

Statistical Power: This calculator uses a fixed 80% power level, which is the standard for most A/B tests and balances the risk of false negatives.

Best Practices for A/B Testing

  • •Run the full duration: Even if you see promising results early, run the test for the full recommended duration to ensure statistical validity.
  • •Include full business cycles: Make sure your test duration includes full business cycles (e.g., weekdays and weekends) to account for traffic variations.
  • •Test one change at a time: To clearly understand what impacts your conversion rate, test one element at a time.
  • •Document everything: Keep detailed records of what you tested, why, and the results for future reference.

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Go beyond calculators

You know when to call it. Now launch it.

Humblytics handles traffic allocation, tracks statistical significance in real-time, and tells you exactly when your test reaches a valid result — no spreadsheets required.

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