Sensitivity and Specificity Calculator
Full diagnostic accuracy panel from four counts.
Enter your values
ⓘ Live results
Results
- Sensitivity (recall)
- 90%
- Specificity
- 94.44%
- Positive predictive value
- 64.29%
- Negative predictive value
- 98.84%
- Accuracy
- 94%
- F1 score
- 0.75
- Positive likelihood ratio
- 16.2
- Youden's index
- 0.8444
Quick answer
Sensitivity is the share of true cases the test catches; specificity is the share of healthy people it correctly clears.
Sensitivity = TP ÷ (TP + FN); Specificity = TN ÷ (TN + FP)
How to use the Sensitivity and Specificity Calculator
- 1Enter the four counts from your validation table.
- 2Read sensitivity and specificity — the test's fixed properties.
- 3Check PPV and NPV, which depend on how common the condition is in your sample.
Worked example
Using the values the calculator loads with:
Inputs
- True positives90
- False negatives10
- False positives50
- True negatives850
Results
- Sensitivity (recall)90%
- Specificity94.44%
- Positive predictive value64.29%
- Negative predictive value98.84%
- Accuracy94%
- F1 score0.75
- Positive likelihood ratio16.2
- Youden's index0.8444
Frequently asked questions
Why do PPV and NPV change between settings?
They depend on prevalence. The same test gives a far lower PPV when screening a healthy population than in a symptomatic clinic.
What is Youden's index for?
A single summary of test usefulness (sensitivity + specificity − 1), often used to pick the best cut-off.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.