Number Needed to Treat (NNT) Calculator

This calculator finds the average number of patients who need to receive a treatment in order to prevent one additional adverse event.

For example, suppose a group of patients is given a new drug, and fewer patients who receive the drug die compared to patients given a placebo. In this case, it’s possible to find just how many patients need to be given the new drug, on average, before one life is saved (i.e. before one patient avoids the adverse event of death). This number is known as the number needed to treat.

To find the number needed to treat, simply enter the values for the control and experimental groups in the boxes below, then click the “Calculate” button.

Bad Outcome Good Outcome
Control Group
Experimental Group

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