Sensitivity & Specificity Calculator
Evaluate the performance of a diagnostic test by entering the true positive, false positive, false negative, and true negative values from a 2×2 contingency table.
Sensitivity & Specificity
intermediateCalculate diagnostic test performance metrics from 2x2 table
Formula
Sens = TP/(TP+FN), Spec = TN/(TN+FP)
Scenario A
How It Works
A 2×2 contingency table compares test results against the true disease status:
| Disease (+) | Disease (−) | |
|---|---|---|
| Test (+) | TP (True Positive) | FP (False Positive) |
| Test (−) | FN (False Negative) | TN (True Negative) |
Sensitivity = TP/(TP+FN) — ability to detect disease when present
Specificity = TN/(TN+FP) — ability to rule out disease when absent
PPV = TP/(TP+FP) — probability disease is present given positive test
NPV = TN/(TN+FN) — probability disease is absent given negative test
Accuracy = (TP+TN)/(TP+TN+FP+FN) — overall proportion correct
Example
A rapid COVID-19 test was evaluated on 200 patients. Results: TP=85, FP=10, FN=15, TN=90.
Sensitivity = 85/100 = 85.0%
Specificity = 90/100 = 90.0%
PPV = 85/95 = 89.5%
NPV = 90/105 = 85.7%
Accuracy = 175/200 = 87.5%
Frequently Asked Questions
What is a good sensitivity value?
For screening tests, high sensitivity (>95%) is preferred to avoid missing cases. For confirmatory tests, high specificity is prioritized. There is always a trade-off between the two.
How does prevalence affect PPV and NPV?
PPV increases with disease prevalence — the same test performs differently in low-prevalence vs high-prevalence populations. This is known as the disease probability paradox.
What is the difference between sensitivity and PPV?
Sensitivity measures how well a test identifies those WITH the disease (test-positive among diseased). PPV measures the probability that a positive test actually means the person has the disease.
Save Configuration Snapshot
Save current parameters to your dashboard for instant one-click reloading.
About This Calculator & Guide
About the Sensitivity & Specificity Calculator
The Sensitivity & Specificity Calculator is a specialized online utility designed to help you calculate diagnostic test performance metrics including sensitivity, specificity, ppv, npv, and accuracy. free online 2x2 table calculator. It performs calculations in real-time to provide immediate, reliable estimates for study, work, or daily tasks.
How to Use
Simply enter your parameters in the input fields of the calculator widget above. The tool evaluates the inputs instantly and displays the results in real-time. You can modify any value to check alternate scenarios and compare figures dynamically.
Data Privacy & Safety
All calculations are executed locally within your web browser. No inputs are sent to our servers or stored externally, ensuring your personal and financial details remain completely private and secure.
FAQ
Frequently Asked Questions
What does the Sensitivity & Specificity Calculator do?+
Calculate diagnostic test performance metrics including sensitivity, specificity, PPV, NPV, and accuracy. Free online 2x2 table calculator. It is designed for quick everyday use and gives clear results without requiring a sign in.
Is the Sensitivity & Specificity Calculator free to use?+
Yes. The Sensitivity & Specificity Calculator is free to use online and works directly in your browser.
Can I use the Sensitivity & Specificity Calculator on mobile?+
Yes. The calculator layout is responsive, so you can use it on phones, tablets, laptops, and desktop screens.