What is the Framingham QTc formula?

QTc = QT + 0.154 × (1 − RR), where QT is in seconds and RR is the R–R interval in seconds (60 ÷ heart rate). The result is then expressed in milliseconds.

How does Framingham differ from Bazett?

Bazett divides QT by the square root of RR, which overcorrects at high heart rates and undercorrects at low rates. Framingham uses a linear additive model, giving more stable results across a wider range of heart rates.

What is a normal QTc value?

Generally, QTc ≤ 440 ms is normal for men and ≤ 450 ms for women. Values between 441–460 ms (men) or 451–470 ms (women) are borderline. Above 460 ms (men) or 470 ms (women) is considered prolonged and warrants further evaluation.

When should I use the Framingham correction?

Framingham is preferred when heart rate is significantly outside the 60–100 bpm normal range, or in population studies. For routine clinical ECG reading, Bazett remains common, but Framingham or Fridericia are increasingly recommended.

Is this tool a substitute for clinical judgment?

No. This calculator is for educational and reference purposes. Clinical decisions about QT prolongation, drug interactions, or arrhythmia risk must be made by a qualified clinician with full patient context.

QTc Framingham Calculator

Enter the measured QT interval and heart rate to get the QTc using the Framingham linear correction formula.

ECG Measurements

QT Interval (ms)

Measured QT from the ECG (typical range 200–600 ms)

Heart Rate (bpm)

Ventricular rate in beats per minute

Biological Sex (for threshold)

Male Female

Interpretation Thresholds

Normal ≤ 440 ms (men) / ≤ 450 ms (women)

Borderline 441–460 ms (men) / 451–470 ms (women)

Prolonged > 460 ms (men) / > 470 ms (women)

Thresholds per AHA/ACC guidelines. Clinical context always applies.

Formula

QTc = QT + 0.154 × (1 − RR)

QT and RR in seconds. RR = 60 ÷ heart rate. Result converted to ms.

Summary

The Framingham QTc formula corrects the measured QT interval for heart rate using a linear model: QTc = QT + 0.154 × (1 − RR), where RR is the R–R interval in seconds. It avoids the overcorrection at high heart rates seen with Bazett's formula and is widely used in epidemiological studies. A QTc above 460 ms (men) or 470 ms (women) is generally considered prolonged.

How it works

Enter the measured QT interval in milliseconds from the ECG tracing.
Enter the heart rate in beats per minute.
The RR interval is computed as 60 000 ÷ heart rate (ms), then converted to seconds.
The Framingham formula is applied: QTc = QT + 0.154 × (1 − RR).
The result is classified as normal, borderline, or prolonged based on standard thresholds.

Use cases

Screen patients for drug-induced QT prolongation before prescribing.
Monitor QTc trends in patients on antiarrhythmic therapy.
Evaluate long QT syndrome risk in cardiology clinics.
Use as an alternative to Bazett's formula when heart rate is outside the 60–100 bpm range.
Support ECG interpretation in emergency and critical care settings.
Research and epidemiological studies where linear correction is preferred.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu