Free Tools
Calculators

A/B Testing Sample Size Calculator

Find the visitors needed per variant before an experiment can detect the lift you care about.

Run tests in Otter A/B

Required sample size

3,843

per variant

Total for A/B

7,686

for control plus one variant

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Duration Calculator

Turn required sample size into a run-time estimate using daily traffic and number of variants.

Significance Calculator

Check completed control and variant counts with a two-sample conversion-rate test.