Survey calculations
Sample size calculator
Estimate how many survey responses you need.
How to use this tool
Set confidence, margin of error and response rate. This model assumes a random sample.
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Your assumptions
Your planning estimate
Estimated margin after rounding: ±4.99 percentage points.
Compare the precision
A smaller margin usually needs more responses. Tap an option to apply it.
These are model estimates, not a promise of completed responses. Finite-population correction is applied when you enter a population.
When this estimate applies
The calculation uses a normal approximation for a proportion and assumes a simple random sample. It does not remove selection bias or nonresponse bias. An opt-in survey panel, convenience sample, weighted survey or clustered design may need a different method or a design-effect adjustment.
For small samples or rare outcomes, get statistical advice before using a normal approximation. The estimated proportion is the share expected to answer a particular way; it is different from the response rate.
Penn State: confidence intervals, sample size and finite populations.
Plan responses and invitations
Enter the population if you know it. Choose confidence, margin and expected response rate, then compare the precision options.
This model assumes a simple random sample. It does not remove nonresponse or selection bias.
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