Method
n₀=z²p(1−p)/e², multiplied by design effect, optionally finite-population corrected, then divided by response rate for invitations.
Math worksheet
Survey Sample Size Calculator
Estimate completed responses and invitations for a proportion, including confidence, margin, finite population, design effect and response rate.
The calculation runs locally. Exact-integer tools avoid floating point; decimal and transcendental tools report rounding limits.
Method and verification guide
How the Survey Sample Size Calculator works
n₀=z²p(1−p)/e², multiplied by design effect, optionally finite-population corrected, then divided by response rate for invitations. The calculator keeps the intermediate values visible so you can reproduce the answer independently.
Interpret the result
The completed sample targets the entered precision under simple random-sampling assumptions; invitations account only for expected nonresponse volume.
Check the assumptions
The formula does not correct selection bias, measurement error, clustering beyond the supplied design effect, or nonrepresentative sampling.
Local calculation
Everything runs in this browser. Inputs are not sent to an external calculator.
Rounding
Displayed values may be rounded for readability while calculations use full floating-point precision unless the tool explicitly uses exact integers.
Scope
The formula does not correct selection bias, measurement error, clustering beyond the supplied design effect, or nonrepresentative sampling.
Simple by design
Three steps to a clearer number.
Enter your details
Use realistic values in each field. You can change them anytime.
Calculate instantly
The formula runs locally, so there is no account or waiting time.
Use the result
Treat the answer as a practical estimate for your next decision.