One-sample chi-square
Find sample size:

If you know the proportion, use this form to find how many subjects you need.
Find effect size:

If you know the number of subjects, use this form to find largest and smallest detectable proportions.
Group proportion:
Comparison proportion:
Click here for sample size:
You will need subjects
Number of subjects:
Comparison proportion:
Click here for effect size:

You can detect p <
You can detect p >
For different power or significance level, change the fields below:
Alpha: Prob(reject H0 when H0 is true)
Power: Prob(reject H0 when H1 is true)
Choose another study design
v. 03/03
Contact: sfh2@columbia.edu
Source: J.L. Fleiss, et al.
Statistical Methods for Rates & Proportions (3rd ed., p. 30)