Free tool

Survey sample size calculator

How many people need to answer your survey before you can trust the result? Pick a confidence level and margin of error and find out.

Survey setup

Defaults — 95% confidence, ±5% margin — fit most surveys.

Confidence level

How sure you want to be that the sample reflects the population.

Margin of error (%)

The ± range around each result. Smaller margin → bigger sample.

Population size — optional

Total people in the group you're surveying. Leave empty if very large or unknown.

Responses needed

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Assumes the most conservative case — a 50/50 answer split (p = 0.5).

This is completed responses. Divide by your expected response rate to know how many people to invite.

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