QTc calculator (four formulas)
Enter the measured QT interval and the heart rate. The calculator gives the corrected QT by Bazett, Fridericia, Framingham and Hodges. Fridericia is preferred at fast or slow rates, where Bazett over- and under-corrects.
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Formulas
| Formula | QTc = |
|---|---|
| Bazett | QT ÷ √RR |
| Fridericia | QT ÷ ∛RR |
| Framingham | QT + 154 × (1 − RR) |
| Hodges | QT + 1.75 × (HR − 60) |
Thresholds
Prolonged: over 450 ms in men, over 470 ms in women. 500 ms or more, or a rise of 60 ms or more from baseline, carries a high risk of torsades de pointes. RR is in seconds (60 ÷ heart rate). With a QRS of 120 ms or more, the JT interval is a better guide.
Frequently asked questions
Which QTc formula is best?
Fridericia and Framingham correct better than Bazett at heart rates outside 60 to 100; Bazett remains common but overestimates QTc at fast rates.
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AI-assisted ECG analysisLast updated 03 November 2026.