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Corrected QT (Fridericia) Calculator

Enter the measured QT interval in ms and the heart rate to get the Fridericia-corrected QTc.

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

The QT interval on an ECG shortens as heart rate rises and lengthens as it slows, so raw QT can't be compared across patients or heart rates without correction. Fridericia's formula corrects for this using a cube root: QTcF = QT ÷ ∛(RR), where RR is the interval between heartbeats in seconds — the same time base used to derive heart rate.

Fridericia's cube-root exponent is a milder correction than Bazett's square-root formula (QTcB = QT ÷ √RR), and clinical studies show it performs more accurately — avoiding Bazett's tendency to overcorrect — at both fast (tachycardic) and slow (bradycardic) heart rates. Cardiologists and QT-monitoring protocols, especially in drug-safety trials evaluating torsades de pointes risk, often prefer Fridericia's correction for this reason.

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