Sample Size Calculator
Two-sample t-Test Paired t-Test Analysis of variance Wilcoxon Test Single proportion Chi-squared Test Fisher's exact Test McNemar's Test Logrank Test Correlation Test
Sample size calculator
Version 1.061


About the Sample Size Calculator

The online Sample Size Calculator was developed and is maintained by Robin Ristl.

I am an academic researcher in statistical methodology and applied statistics based in Vienna, Austria. I prepared the online Sample Size Calculator to fit the needs of researchers such as myself in designing medical and other scientific studies. The calculator includes many advanced options, which I observed to be of use, such as accounting for drop-outs or planning for unequally sized groups.

Feedback on the calculator comes form resarchers around the world. I am confident it fits well to the needs of other applied statisticians and all researchers planning quantitive research.


If you require advice regarding your sample size planning, or if you have a question regarding underlying functions or how to use the calculator, get in contact with:


This is the online Sample Size Calculator version 1.061.

Terms of Use

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Disclaimer of Warranties

This website and the online Sample Size Calculator with all available functions and all included services are provided “as is” and “as available”. The maintainer of the website and of the provided software and services does not make any express or implied warranties of any kind. In particular, but not limited to, there are no warranties that the software and services are free of errors or defects, there are no warranties of fitness for a particular purpose, of merchantability, of non-infringement, and no warranties that access to or use of the software or services will be uninterrupted or error-free or that defects in the software or services will be corrected. Your use of the website and the provided software and services is at your own risk.

Limitations of Liability

The maintainer of the website shall under no circumstances be liable for any direct, indirect, incidental, consequential, or exemplary damages. This shall include, but not be limited to, damages for loss of profits, business interruption, business reputation or goodwill arising out of the use of or the inability to use the software and services or any modification or interruption or termination of the website or of any included services.