NNT
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The Number Needed to Treat (NNT) calculator is a statistical tool that helps determine the number of patients that need to be treated to prevent a certain number of adverse events. It is commonly used in clinical research and medicine to evaluate the effectiveness of a treatment.
The formula used to calculate NNT is based on the odds ratio of adverse events between the treated group and the placebo group. It is calculated as follows: NNT = 1 / (RR - 1), where RR is the relative risk ratio.
The NNT is important for healthcare professionals and patients to make informed decisions about the benefits and risks of a treatment. It is recommended to use the NNT calculator in clinical studies and in situations where it is necessary to evaluate the effectiveness of a treatment.
Additionally, it is important to be cautious when the NNT is very high or very low, as this may indicate that the treatment is very effective or very ineffective.
Frequently asked questions
What is the Number Needed to Treat (NNT)?
The NNT is the number of patients that need to be treated to prevent a certain number of adverse events. It is calculated based on the odds ratio of adverse events between the treated group and the placebo group.
When should the NNT calculator be used?
The NNT calculator should be used in clinical studies and in situations where it is necessary to evaluate the effectiveness of a treatment. Additionally, it can be useful for healthcare professionals and patients to make informed decisions about the benefits and risks of a treatment.
What does a very high or very low NNT mean?
A very high NNT may indicate that the treatment is very effective, while a very low NNT may indicate that the treatment is very ineffective. It is essential to be cautious in these cases and evaluate the effectiveness of the treatment with caution.
How is the NNT calculator calculated?
The NNT calculator is calculated based on the formula NNT = 1 / (RR - 1), where RR is the relative risk ratio.
Is the NNT relevant to all treatment situations?
No, the NNT is more relevant to situations where it is necessary to evaluate the effectiveness of a treatment in relation to adverse events. In other situations, other measures of effectiveness may be more relevant.