QTc Calculator

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Enter the QT directly in ms, or count small boxes on the ECG paper grid.
Measured QT interval from the ECG, in milliseconds (typically 350-450 ms).
ms
Provide the heart rate, or the measured RR interval between beats.
Ventricular heart rate in beats per minute. RR interval is derived as 60000 / heart rate.
bpm
Bazett is the classic correction. Fridericia and Rautaharju perform better at extreme rates.
Prolongation thresholds differ slightly by sex (>=450 ms male, >=460 ms female).
Corrected QT (QTc)Normal QTc
400ms
InterpretationNormal
Heart rate60bpm
RR interval1,000ms
Bazett QTc400ms
Fridericia QTc400ms
Framingham QTc400ms
Hodges QTc400ms
Rautaharju QTc400ms
400 ms
Normal<430Borderline430-450Prolonged450-500Markedly500+

Your Bazett-corrected QTc is about 400 ms (male threshold >=450 ms).

  • QTc adjusts the raw QT interval for heart rate so values can be compared across different pulses.
  • A QTc of 500 ms or more is associated with a markedly higher risk of torsades de pointes and warrants prompt attention.
  • At this slow heart rate, Bazett tends to under-correct, so cross-check the Fridericia value shown below.

Next stepConfirm the QT measurement on the ECG and discuss any prolonged result with a clinician.

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