Experimental Design

Animal Sample Size Calculations

Proper sample size calculation is both a scientific and ethical imperative (1).

Researchers are routinely asked to justify the number of animals used in their studies by CULATR, funding agencies or, increasingly, by journal editors (1).

In accordance with the 3R's, studies should be designed to reduce the number of animals used to meet scientific objectives. While the ethical reasons underlying such reductions are obvious, it is also ethically important to rigorously test experimental hypotheses when the results may directly impact human health (1).

Underpowered studies that do not include enough animal subjects may produce ambiguous or misleading results, failing to promote scientific progress or the reproducibility of research findings. As such, underpowered studies unnecessarily subject animals to experimentation and violate the 3R’s principles (1).

Below is a basic Sample Size Calculator that will assist you in estimating the number of animals needed in each group.

Typically a Power of between 80% and 90% is adequate for animal studies. The Calculator will give you an estimate of animal numbers both at 80% and 90% Power.

If adequately Powered, controlled, blinded and randomised, as with Human Clinical Trials, repeating of studies is NOT necessary.

(1) Extracted from an article written by Philip Dubé, PhD, Thursday, December 21, 2017. Read the full article at:



Power & Animal Number Calculator

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