Sensitivity and Specificity Calculator
Evaluate a test using true and false positives and negatives.
Your numbers
Your results
Sensitivity and Specificity Calculator by TheCalcTools
How the Sensitivity and Specificity Calculator works
Enter the counts from your test results compared against the true condition.
Sensitivity is the share of people with the condition who test positive.
Specificity is the share without the condition who test negative.
The formula
Worked example
Using the default values shown in the calculator:
| True positives | 90 |
|---|---|
| False positives | 30 |
| False negatives | 10 |
| True negatives | 870 |
- Sensitivity = 90 ÷ 100 = 90.0%.
- Specificity = 870 ÷ 900 = 96.7%.
- PPV = 90 ÷ 120 = 75.0%.
Result:
| Sensitivity | 90.00% |
|---|---|
| Specificity | 96.67% |
| Positive predictive value | 75.00% |
| Negative predictive value | 98.86% |
| Accuracy | 96.00% |
| Positive likelihood ratio | 27.00 |
Frequently asked questions
Why does PPV depend on prevalence?
When a condition is rare, even a specific test produces many false positives compared with true positives, which lowers PPV.
What is a good sensitivity?
It depends on the use. Screening tests aim for high sensitivity so few cases are missed; confirmatory tests aim for high specificity.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.