Sensitivity Calculator

Created by Anna Szczepanek, PhD
Reviewed by Steven Wooding
Last updated: Oct 31, 2022

Omni's sensitivity calculator is here if you need to estimate how well a diagnostic test can identify true positive cases. We'll discuss what the sensitivity of a test is, what the sensitivity equation looks like, and how to calculate sensitivity both by hand and with the help of our calculator.

What is the sensitivity equation?

Sensitivity is the proportion of people who have the disease and tested positive among those who have the disease regardless of whether they tested positive or negative, i.e., among true positive cases and false negative cases.

Therefore, the sensitivity equation is:

Sensitivity = TP / (TP + FN),

where TP is true positives and FN is false negatives. In other words, sensitivity is the probability of having a positive test, conditioned on being sick.

How do I interpret test sensitivity?

If a test has high sensitivity, then a sick person has a high probability of getting a positive test result. Hence, if you get a negative result in a test with high sensitivity, then it's very probable you do not have the disease. However, if you get a positive result (still in a test with high sensitivity), then you do not necessarily need to worry! This is because sensitivity does not take into account false positives.

⚠️ Extreme example: Imagine a test that always gives a positive result. Its sensitivity is 100% (all sick people will get a positive result). However, all healthy people will get a positive result as well! This test is completely useless despite having 100% sensitivity.

As you can see, calculating sensitivity is straightforward, at least in theory. However, with actual data it may get complicated. But, hey, our sensitivity calculator is here to help!

How to use this sensitivity calculator?

To most efficiently use our sensitivity calculator, follow these steps:

  1. Input data: the number of true positives and false negatives.

  2. The sensitivity of your test gets computed immediately!

  3. There are also fields dedicated to computing specificity, in case you need it (and have the necessary data).

  4. Need even more coefficients? Click the advanced mode and enjoy!

We've built several tools related to the confusion matrix and test accuracy:

FAQ

How do I calculate sensitivity?

To calculate sensitivity, you need to:

  1. Know the number of true positive cases TP.

  2. Know the number of false negative cases FN.

  3. Compute the number of sick people: TP + FN.

  4. Compute sensitivity equation:

    Sensitivity = TP / (TP + FN).

Anna Szczepanek, PhD
table for sensitivity and specificity
Sensitivity
True positive
False negative
Sensitivity
%
Specificity
True negative
False positive
Specificity
%
Extra
For more results, click the advanced mode below.
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