How to Use the A/B Test Duration Calculator
Before launching an A/B test, knowing how long it needs to run for reliable results helps you plan your campaign timeline. This calculator computes the statistically required sample size, then divides it by your daily visitors to get the minimum test duration.
The minimum detectable effect (MDE) is the smallest improvement you consider meaningful. A lower MDE requires detecting a finer difference, which increases the required sample size and duration.
Low-traffic pages can produce long durations. In that case, consider raising the MDE or lowering confidence to shorten the test — or commit to the full planned duration to keep results trustworthy.
Frequently Asked Questions
Not recommended. Stopping before reaching the target sample size based on interim results introduces statistical error (peeking bias) and can lead to incorrect conclusions.
Yes — even if the calculated duration is under 7 days, running for at least 1-2 weeks and covering at least one full weekly cycle reduces day-of-week bias.