How this calculator works
QT correction estimates how ventricular repolarization duration would compare at a reference heart rate. These four equations use RR in seconds and QT in milliseconds as labelled. Bazett can overcorrect at fast rates and undercorrect at slow rates. Wide QRS complexes, pacing, irregular rhythms and difficult T-wave endpoints require specialist interpretation; the page does not select a diagnosis or medication decision. The result is an estimate for information only and is not medical advice.
Formula
Bazett: QT/√RR. Fridericia: QT/∛RR. Framingham: QT + 154(1-RR). Hodges: QT + 1.75(HR-60). QT and QTc in ms; RR in s; HR = 60/RR.
Worked example
QT 400 ms at RR 1 s gives 400 ms with all four equations. QT 320 ms at RR 0.64 s gives Bazett 400 ms and Framingham 375.44 ms.
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Frequently asked questions
Why do the results differ?
Each equation corrects the QT-rate relationship differently, especially away from 60 beats/min.
Are milliseconds and seconds interchangeable?
Only with conversion. QT fields here use ms and RR uses seconds.
Should I act on a result alone?
No. Measurement quality, symptoms, electrolytes and medicines require professional review.