About this QTc Calculator
The QT interval represents the time it takes for the heart ventricles to depolarize and repolarize. Because this duration changes with heart rate, it must be 'corrected' (QTc) to standardize the measurement for clinical assessment.
Who this calculator is for
- Clinicians, pharmacists, and trainees reviewing ECG measurements and medication risk.
- People who already have a measured QT interval and heart rate from an ECG.
- Anyone comparing Bazett, Fridericia, and Framingham correction methods.
When to use it
- Use this calculator when charting or double-checking a manually measured QT interval.
- Use it to compare how different formulas behave at faster or slower heart rates.
- Use it when discussing medication-related QT prolongation in an educational setting.
How to use this calculator
- Measure the QT Interval from the start of the Q wave to the end of the T wave.
- Enter the patient's current Heart Rate.
- View results for Bazett (standard), Fridericia, and Framingham formulas.
Key assumptions
- The calculation assumes the QT interval was measured accurately from a readable ECG.
- Each correction formula has known strengths and weaknesses at very fast or very slow heart rates.
- QTc is a screening aid and should be interpreted with symptoms, rhythm context, medications, and electrolytes.
Accuracy and testing
Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.
Key Features
- Calculates 3 common formulas simultaneously
- Automatic RR conversion
- Clinical safety range indicators
Things to Keep in Mind
Not for diagnostic use. Automated calculations should always be verified by a qualified professional. T-wave morphology can affect manual measurement accuracy.