Latest Cancer TreatmentsDr. Mohammadreza Dabiri
Dr. Mohammadreza Dabiriفارسی
Clinical tool

NNT, Absolute and Relative Risk Reduction Calculator

Reading trial results: how many patients must be treated for one to benefit?

Updated: 27 October 20261 min read1 reference

From the event rates (e.g., death or relapse) in the two arms of a study, calculates the absolute and relative risk reduction and the number needed to treat (NNT).

This calculator needs JavaScript; the formula and its interpretation are in the text of this page.

An aid for clinicians; it does not replace clinical judgement, local protocols or the drug label. Double-check every result before prescribing.

Why NNT?

A relative risk reduction (e.g., “25% lower”) is misleading without the baseline risk; the absolute risk reduction and NNT show how many patients actually benefit [1]. NNT = 100 ÷ absolute risk reduction (in percentage points) and always depends on the follow-up time of the study.

For critical reading of trials: reading trials and biomarkers lesson.

References

1 reference
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Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.

  1. 1
    An assessment of clinically useful measures of the consequences of treatmentLaupacis A, Sackett DL, Roberts RS · N Engl J Med · 1988;318:1728-33
    DOIPubMed Back to text

This page is based on reputable scientific sources and was last updated on 27 October 2026. The content of this website is for educational and informational purposes only and does not replace consultation, diagnosis or treatment by a specialist physician. Consult your treating physician about any treatment decision.

Printed from the website; the full and up-to-date version: https://drdabiri.com/en/tools/nnt-calculator/

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