सैंपल साइज़ कैलकुलेटर.

Assumes random samples. More than two variants use a Bonferroni-corrected significance level. Everything is calculated in your browser; nothing you type is uploaded.

A/B: the standard two-proportion formula. Survey: n₀ = z² p (1 − p) ÷ e² with the finite population correction.

With a 5 % baseline and a 10 % relative lift at 95 % confidence and 80 % power, you need 31,234 visitors per variant; a survey at ±5 % needs 385 responses.