Statistics

Sample Size Calculator

Sample size for a proportion estimate.

Free to use — no sign-up or login.

Sample size n

This free Sample Size Calculator covers Sample size for a proportion estimate.

n = z² p (1−p) / e² for a proportion. Related statistics tools sit beside How it works, with no account required.

Using the Sample Size Calculator

Sample size for a proportion estimate. Typical inputs are Expected proportion (%), Margin of error (%) and z. How it works beside the form states the identity the Sample Size Calculator applies.

FAQ

How do I use the Sample Size Calculator?

Open the Sample Size Calculator, fill Expected proportion (%), Margin of error (%) and z, and read the result. Enter Expected proportion (%), Margin of error (%), and z for the Sample Size Calculator; enter percentage fields as percentage points. The calculator reports Sample size n: n = z² p (1−p) / e² for a proportion. Expected proportion and Margin of error must be entered as percentages, with a positive margin.

What formula does the Sample Size Calculator use?

The Sample Size Calculator uses the identity in How it works. In words: Enter Expected proportion (%), Margin of error (%), and z for the Sample Size Calculator; enter percentage fields as percentage points. The calculator reports Sample size n: n = z² p (1−p) / e² for a proportion. Expected proportion and Margin of error must be entered as percentages, with a positive margin.