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Clinical & Lab Medicine Established ECG correction formulas Source-mapped educational ECG calculator Higher-risk clinical context

QTc Calculator

Calculate corrected QT interval from QT duration and heart rate using common correction formulas.

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Interactive tool

Calculator

Enter values carefully. Results appear after calculation and should be interpreted with the safety notes and source method on this page.

Source-mapped educational ECG calculator

Step 1 — Enter inputs

4 fields required for this tool

Step 2 — Review the result

The result area updates below and keeps safety wording visible.

Result

Complete the form and select Calculate.

About this calculator

The QTc calculator estimates the heart-rate corrected QT interval from a measured QT interval and heart rate. It shows several common correction formulas because QTc interpretation can vary by formula and heart rate.

Source-backed
RR = 60 / heart rate. Bazett QTc = QT / √RR; Fridericia QTc = QT / RR^(1/3); Framingham QTc = QT + 0.154 × (1 − RR); Hodges QTc = QT + 1.75 × (heart rate − 60).
Review status
Source-mapped educational ECG calculator
Limitations
QTc formulas depend on accurate QT and RR/heart-rate measurement and may be unreliable with bundle branch block, paced rhythm, atrial fibrillation, very high or low heart rates, or poor ECG quality.

Formula and method

RR = 60 / heart rate. Bazett: QT/√RR. Fridericia: QT/RR^(1/3). Framingham: QT + 0.154 × (1 − RR). Hodges: QT + 1.75 × (heart rate − 60).

Medical safety note: This page is for education only and should not replace professional medical advice. For emergencies, medication decisions, or severe symptoms, contact a qualified clinician or local emergency service.

Limitations and when not to rely on this result

  • QTc formulas depend on accurate QT and RR/heart-rate measurement and may be unreliable with bundle branch block, paced rhythm, atrial fibrillation, very high or low heart rates, or poor ECG quality.
  • Medication decisions, syncope, electrolyte disorders, congenital long-QT concerns, or very prolonged QTc require clinician review.
  • Use this page for calculation support only, not emergency ECG interpretation.

Frequently asked questions

What is QTc? +

QTc is the QT interval corrected for heart rate. It is used when reviewing ECGs for possible QT prolongation.

Which QTc formula should I use? +

Bazett is common, but Fridericia, Framingham, and Hodges may perform differently at heart-rate extremes. Clinicians choose based on context.

Is a long QTc dangerous? +

A prolonged QTc can be associated with arrhythmia risk, especially with symptoms, electrolyte problems, overdose, or QT-prolonging medications.

Can this diagnose long QT syndrome? +

No. It only calculates QTc from entered values. Diagnosis requires ECG quality review, history, medications, electrolytes, and clinician assessment.

Why does heart rate matter? +

The measured QT interval changes with heart rate, so correction formulas estimate what the QT might be at a standardized rate.