Corrected QT (QTc) Calculator
The QT interval on an electrocardiogram (ECG) varies with heart rate, so it needs to be corrected for accurate clinical assessment. Enter your measured QT interval and heart rate to calculate the corrected QT using both Bazett's and Fridericia's formulas.
The QT interval represents the time it takes for the heart's ventricles to depolarize and repolarize, measured from the start of the Q wave to the end of the T wave on an ECG. Because this interval naturally shortens at faster heart rates and lengthens at slower rates, raw QT values are not directly comparable between patients with different heart rates. Corrected QT (QTc) formulas adjust for this rate dependence.
Bazett's formula (QTc = QT / sqrt(RR)) is the most widely used correction and remains the standard in most clinical settings. However, it tends to overcorrect at high heart rates and undercorrect at low heart rates. Fridericia's formula (QTc = QT / RR^(1/3)) handles extreme heart rates more accurately and is now preferred by the FDA for drug safety studies and by many electrophysiologists.
A prolonged QTc (generally >470 ms in men or >480 ms in women) increases the risk of a dangerous ventricular arrhythmia called torsades de pointes. Many medications, electrolyte imbalances, and inherited conditions (long QT syndrome) can prolong the QT interval. Monitoring QTc is a routine part of cardiac care and drug safety assessment.
DISCLAIMER: This calculator is for educational reference only. QT interval measurement and clinical interpretation should be performed by qualified healthcare professionals. Do not make treatment decisions based solely on this tool.