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Research sample size calculator

Work out how many survey responses you need at your confidence and margin, then convert that to invitations at your expected response rate.

Set your confidence, margin, and population to size the study.

This sizes a one-shot survey or study with Cochran's formula and the finite population correction. It is not an A/B test power calculation: experiments compare two variants and need different math. The 50 percent default is the worst case for a proportion, and a range divided by 4 is a common stand-in for an unknown standard deviation. When invitations pass half the population, just survey everyone; the result says so.

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Research sample size calculator

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