QTc calculator
Correct the QT interval for heart rate with the Bazett and Fridericia formulas.
Your result appears here as you type.
The formulas
- Bazett: QTc = QT ÷ √RR.
- Fridericia: QTc = QT ÷ ∛RR.
- RR is the interval between beats in seconds: 60 ÷ heart rate.
Usual limits
| QTc | Meaning |
|---|---|
| Up to 450 ms in men, 460 ms in women | Within the usual limit |
| Above that | Prolonged |
| 500 ms and above | Markedly prolonged, with higher risk of torsades de pointes |
Which formula to use
Bazett over-corrects at fast heart rates and under-corrects at slow ones. Fridericia is often preferred away from about 60 to 100 bpm.
What to do next
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See the featuresCommon questions
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What is a normal QTc?
Commonly up to 450 ms in men and 460 ms in women. Limits vary slightly between guidelines.
Should I use Bazett or Fridericia?
Bazett is the most widely quoted. Fridericia is often preferred at fast or slow heart rates. This calculator shows both.
Try it with next week’s patients
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