Corrected QT Interval (QTc) Calculator
Calculate the corrected QT interval using Bazett, Fridericia, Framingham, and Hodges formulas from QT interval and heart rate.
Medical Disclaimer
This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.
Inputs
Normal QT: 350–440 ms; prolonged QTc: >450 ms (male) or >470 ms (female) per AHA
Normal HR: 60–100 bpm; Bazett formula most accurate 60–100 bpm (less so at extremes)
Results
QTc (Bazett)
438ms
QTc (Fridericia)
425ms
How to Use This Calculator
- Enter the measured QT interval (ms) and heart rate (bpm).
- Review QTc by Bazett, Fridericia, Framingham, and Hodges formulas.
- Bazett is most widely used clinically; Fridericia is preferred at extreme heart rates.
- QTc > 500 ms by any formula is critically prolonged.
How the result changes with QT Interval
| QT Interval | QTc (Bazett) | QTc (Fridericia) |
|---|---|---|
| 250 | 274ms | 266ms |
| 375 | 411ms | 398ms |
| 525 | 575ms | 558ms |
| 650 | 712ms | 691ms |
What each input means
- QT Interval
- Measured QT interval from the 12-lead ECG in milliseconds. Normal QT: 350–440 ms. Prolonged QTc (>450 ms men, >470 ms women) increases torsades de pointes risk.
- Heart Rate
- Heart rate in beats per minute for RR interval calculation. RR interval (seconds) = 60 ÷ heart rate. Bazett formula: QTc = QT ÷ √RR. Most accurate at heart rates 60–100 bpm.
How this is calculated
Worked example, using the default values
- Identify Input ParametersQT Interval = 400, Heart Rate = 72 = 2 input(s) provided
- Calculate QTcQTc438 = 438
- Calculate QTcQTc425 = 425
- Calculate QTcQTc426 = 426
- Calculate QTcQTc421 = 421
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