Doctoral Edge Services Calculate sample size
For MD, MS and PhD researchers

Plan your study with numbers you can defend.

Calculate your sample size with a guided calculator. Every number comes from tested formulas, and every write-up arrives with the full working and references, ready for your synopsis.

Calculate sample size How it works

Free to use. No sign-up. No patient data needed.

Example result Single proportion
173 participants

Prevalence 27% (Kumar et al., 2024), precision ±7%, 95% confidence: 155 from the formula, 173 after 10% non-response.

Sample-size-thyroid-ACS.docx
Formula, every step and 2 references, in your thesis font and margins

One place for every stage of your thesis

Start with sample size today. New tools will join the same website, so your topic and numbers carry forward from one step to the next.

Available now

Sample size calculator

Nine study designs, every working step, honest feasibility checks and a Word write-up with references.

Chat assistant coming soon. Open the calculator
Coming next

Synopsis writer

Turns your topic, objectives and sample size into a synopsis draft in your university's format.

Planned

Data analysis

Upload your data; the right test runs, assumptions are checked and the results are written up.

Planned

Thesis chapters

Introduction, review of literature, methods, results and discussion, with every citation checked against PubMed.

Planned

Journal paper

A manuscript in IMRaD format, built from your thesis and formatted for the journal you choose.

Planned

Poster and slides

A conference poster and a presentation, made from the same results and references.

From topic to Word file in three steps

  1. Describe your study

    Type your topic. The calculator suggests a study design and shows why, or you pick one from the list.

  2. Enter values from published research

    Add the expected value from a similar published study, with its reference. Search links to PubMed and Google Scholar are built in.

  3. Download the write-up

    Formula, steps, final number and references in Word, in your university's font, size and margins.

Numbers your examiner can check

Tested formulas

Charan & Biswas, Kelsey, Fleiss, Buderer and others, checked against hand calculations and published tables.

Every step shown

The write-up shows the formula, each input with its source, and every line of the calculation.

Honest when patients are few

If your hospital sees fewer patients, the calculator shows the precision or power you can achieve, instead of bending the formula.

Made by a medical statistician

Designed around the questions postgraduate students bring to a statistics department every week.

Common questions

Is the calculator free?

Yes. The sample size calculator is free and needs no account.

Where do I get the expected values?

From a published study similar to yours: the prevalence, mean, standard deviation or odds ratio it reports. Cite that study in your synopsis; the calculator adds it to the reference list.

Can I use the write-up in my synopsis or thesis?

Yes. Download it as a Word file, and check the design and values with your guide before you submit.

Is my data stored?

No. The calculator runs in your browser. Your values are saved only on your own device, so they are still there when you come back.

What if I can enrol only a limited number of patients?

Choose “What my patients allow”. The calculator works out the precision or power that number gives and writes it up as a limitation, instead of changing your inputs.