About the A/B Test Duration Calculator
How many days to run an A/B test to reach the required sample size, given daily traffic and number of variants.
Also known as: ab test length, how long to run ab test, experiment duration.
How to use this calculator
- Enter baseline conversion rate, relative lift to detect, daily visitors (total), variants (incl. control).
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
n = (z_α/2·√(2p̄q̄) + z_β·√(p₁q₁ + p₂q₂))² / (p₂ − p₁)²
Worked example
Using the values pre-filled in the calculator above:
- Baseline conversion rate = 3 %
- Relative lift to detect = 10 %
- Daily visitors (total) = 2,000
- Variants (incl. control) = 2
the calculator returns:
- Duration: 54 days
- Visitors per variant: 53,211
- Total visitors: 106,422