Sensitivity and Specificity Calculator
Full diagnostic accuracy panel from four counts.
Enter your values
Enter the true positives you are working with.
Enter the false negatives you are working with.
Enter the false positives you are working with.
Enter the true negatives you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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)
At a glance
| What it does | Full diagnostic accuracy panel from four counts. |
|---|---|
| Category | Statistics |
| Inputs needed | True positives, False negatives, False positives, True negatives |
| Main output | Sensitivity (recall) |
| Formula | Sensitivity = TP ÷ (TP + FN); Specificity = TN ÷ (TN + FP) |
| Cost | Free — no sign-up, no download |
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.
Inputs explained
- True positives
- Enter the true positives you are working with.
- False negatives
- Enter the false negatives you are working with.
- False positives
- Enter the false positives you are working with.
- True negatives
- Enter the true negatives you are working with.
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.
What do I need to enter into the Sensitivity and Specificity Calculator?
Just 4 values: true positives, false negatives, false positives, true negatives. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Sensitivity and Specificity Calculator work out the answer?
Sensitivity is the share of true cases the test catches; specificity is the share of healthy people it correctly clears. It applies the formula Sensitivity = TP ÷ (TP + FN); Specificity = TN ÷ (TN + FP) and shows the working so you can check each step by hand.
Is the Sensitivity and Specificity Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.