Calculate the corrected QT interval using Bazett, Fridericia, and Framingham formulas. Enter the measured QT interval and heart rate from an ECG to assess QT prolongation risk.
Measured from ECG
QTc (Bazett)
438 ms
QTc (Fridericia)
425 ms
QTc (Framingham)
426 ms
Interpretation (Bazett)
Normal QTc interval.
Normal: ≤450 ms (male) | Prolonged: 451–500 ms | High risk: >500 ms
Normal QTc interval. No increased risk of torsades de pointes from QTc prolongation.
QT / RR^0.5
Most widely used. Overcorrects at high HR, undercorrects at low HR.
QT / RR^(1/3)
Preferred for HR outside 60-100 bpm range. Better accuracy at extreme rates.
QT + 0.154(1-RR)*1000
Linear correction. Regression-based from Framingham Heart Study.
The QT interval represents the total time for ventricular depolarization and repolarization on an electrocardiogram. A prolonged QTc is a significant clinical concern because it predisposes patients to dangerous arrhythmias. Many common medications — including certain antibiotics, antipsychotics, antiemetics, and antiarrhythmics — can prolong the QT interval. Regular monitoring of the QTc is an important nursing responsibility when these medications are administered.
The QTc is the QT interval adjusted for heart rate. The QT interval on an ECG represents ventricular depolarization and repolarization. Since QT naturally shortens at higher heart rates and lengthens at lower rates, correction formulas normalize the value to allow comparison across different heart rates.
A prolonged QTc interval increases the risk of a life-threatening ventricular arrhythmia called torsades de pointes, which can degenerate into ventricular fibrillation and sudden cardiac death. Many medications can prolong the QT interval, making monitoring essential.
Bazett's formula is the most widely used and referenced in drug labeling. However, it tends to overcorrect at high heart rates and undercorrect at low heart rates. Fridericia's formula is considered more accurate at extreme heart rates and is increasingly preferred in clinical research.
Mean Arterial Pressure Calculator
Calculate MAP from systolic and diastolic blood pressure readings. Get instant clinical interpretation of the result to assess perfusion status.
ABG Interpreter
Enter arterial blood gas values to quickly identify acid-base imbalances. Get interpretation of the primary disorder, compensation status, and oxygenation assessment.