Sample size calculator

Describe your study, enter the expected values from published research, and get the full calculation written out for your synopsis, with references, ready to download as a Word file.

No values yet? The sample size assistant finds them in published studies for you.

Your study

Thesis or synopsis topic

What is the main aim of your study?

Values

Sample size I need What my patients allow

Confidence level

Power

Where these values come from

In-text citation

Full reference (Vancouver)

Find a published value: Search PubMed ↗ Google Scholar ↗

Adjustments

Expected non-response or drop-out

Reason, as written in the synopsis

Design effect Only for cluster sampling (often 1.5–2). Leave blank otherwise.

Total eligible population Applies the finite population correction when the whole group is small and known.

Z values

Table values (1.96, 0.842), as written in most synopses Exact values (1.959964, 0.841621), as used by OpenEpi and G*Power

Write-up

Formatting applies to the Word file

Font

Size

Line spacing

Space after

Text

Paper

Margins

Top (in)

Bottom (in)

Left (in)

Right (in)

Formulas: single proportion and single mean (Charan & Biswas, 2013); two proportions, case-control and cohort (Kelsey et al., 1996; Fleiss et al., 2003); two means and paired means (Chow et al., 2008); correlation (Hulley et al., 2013); diagnostic accuracy (Buderer, 1996); finite population correction (Cochran, 1977); feasibility justification (Lakens, 2022). Every result rounds up to whole participants.

Check the design and the expected values with your guide or the department statistician before submitting.