Corrected QT Interval (QTc)



QTc Bazett[1]:
QTc Fredericia[2]:
QTc Framingham[3]
QTc Hodges[4]:

Computational notes

When you enter QT or RR in millimeters, it is assumed that the ECG is recorded at a speed of 25mm/sec.

With QT expressed in seconds, and Heart Rate (HR) in beats per minute:

RR interval (sec) = 60 / HR.

QTc Bazett:[1]

QTc - Bazett formula

QTc Fridericia:[2]

QTc - Fridericia formula

QTc Hodges:[3]

QTc - Hodges formula

QTc Framingham:[4]

QTc - Framingham formula


  1. Bazett HC (1920) An analysis of the time-relations of electrocardiograms. Heart 7:353-370.
  2. Fridericia LS (1920) Die Systolendauer im Elektrokardiogramm bei normalen Menschen und bei Herzkranken. [The duration of systole in the electrocardiogram of normal subjects and of patients with heart disease.] Acta Medica Scandinavica 53:469–486.
  3. Hodges M, Salerno D, Erlien D (1983) Bazett's QT correction reviewed. Evidence that a linear QT correction for heart is better. J Am Coll Cardiol 1:694.
  4. Sagie A, Larson MG, Goldberg RJ, Bengtson JR, Levy D (1992) An improved method for adjusting the QT interval for heart rate (the Framingham Heart Study). Am J Cardiol 70:797–801.

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