Calculate QTcF with the Fridericia formula: enter the measured QT interval and the heart rate or RR interval to get the corrected QT in milliseconds.

Interpretation and display
No automatic normal or abnormal bands are applied.

Optional. Use a limit applicable to the correction formula and patient; blank means no comparison.

Medical note: This calculator is for educational use and is not medical advice. QT/QTc measurement and interpretation should be done by a qualified clinician and depend on factors like ECG technique, medications, electrolytes, age, and sex. If you have fainting, seizures, chest pain, severe dizziness, or palpitations, seek urgent medical care—do not use this tool to adjust medications.

Fridericia QTc Formula

The following formula is used to calculate the corrected QT interval (QTc) using the Fridericia method.

QTc = (QT) / ((RR)1/3) = QT × ((HR) / (60))1/3

Variables:

  • QTc is the corrected QT interval (milliseconds)
  • QT is the measured QT interval (milliseconds)
  • RR interval is the time between heartbeats, calculated as 60 / heart rate (seconds)

To calculate the corrected QT interval (QTc) using the Fridericia formula, divide the measured QT interval by the cube root of the RR interval in seconds (or equivalently multiply QT by the cube root of HR/60).

What is the Fridericia QTc?

The Fridericia QTc is a formula used to correct the QT interval for heart rate variability. The QT interval is the time from the start of the Q wave to the end of the T wave in the heart’s electrical cycle. A prolonged QT interval can be a risk factor for ventricular arrhythmias. Fridericia is one of several heart-rate correction methods. Its result is not a diagnosis; ECG measurement, rhythm, QRS duration and clinical context affect interpretation.

How to Calculate Fridericia QTc?

The following steps outline how to calculate the Fridericia Corrected QT Interval (QTc).

  1. First, measure the QT interval (QT) in milliseconds.
  2. Next, measure the heart rate in beats per minute.
  3. Calculate the RR interval in seconds as 60 divided by the heart rate.
  4. Use the Fridericia formula: QTc = QT / (RR interval in seconds)(1/3).
  5. Finally, calculate the corrected QT interval (QTc) in milliseconds.
  6. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

QT interval (QT) = 360 milliseconds

Heart rate = 75 beats per minute