QTc Calculator (Corrected QT Interval)

QTc Calculator (Corrected QT Interval). The QT interval on an ECG varies with heart rate, so clinicians use the QTc (Corrected QT Interval) to assess whether cardiac repolarization is truly prolonged — a risk factor for dangerous arrhythmias. Enter your QT interval (in milliseconds) and heart rate (in bpm), then select a correction formula (Bazett, Fridericia, Framingham, or Hodges) and gender to get the corrected QT interval. Secondary outputs include the RR interval, clinical interpretation, and the normal QTc range for your gender. Also try the calculate Expected pCO₂ (Midpoint), Expected pCO₂ — Lower Bound & Expected pCO₂ — Upper Bound — Winter's Formula.

Results

Corrected QT Interval (QTc)

RR Interval

Clinical Interpretation

Normal Range for Gender

What is the QTc interval and why is it important?

The QTc (corrected QT interval) is a measure of the time it takes for the heart's ventricles to repolarize, adjusted for heart rate. It's crucial for assessing the risk of dangerous arrhythmias and sudden cardiac death. See also our Body Surface Area — Body Surface Area (BSA).

What is considered a normal QTc interval?

Normal QTc values are typically less than 440 msec for men and less than 460 msec for women. Values above 450 msec (men) or 470 msec (women) may indicate prolonged QT syndrome.

Which QTc correction formula is most accurate?

Bazett's formula is most commonly used but may overcorrect at high heart rates. Fridericia's formula is more accurate at extreme heart rates, while Framingham and Hodges formulas may be better for specific populations.

What medications can prolong the QTc interval?

Many medications can prolong QTc including certain antibiotics, antiarrhythmics, antipsychotics, and antidepressants. Always check drug interactions and monitor QTc when prescribing these medications.

When should QTc monitoring be performed?

QTc monitoring should be done when starting QT-prolonging medications, in patients with cardiac conditions, electrolyte imbalances, or family history of sudden cardiac death.

What factors can affect QTc measurements?

QTc can be affected by electrolyte imbalances (especially potassium and magnesium), medications, heart disease, age, gender, and genetic conditions like long QT syndrome.

How accurate is this QTc calculator for clinical decisions?

This calculator provides accurate QTc calculations using standard formulas. However, clinical decisions should always involve proper ECG interpretation by qualified healthcare professionals and consideration of the patient's overall clinical context. You might also find our Blood Alcohol Content (BAC) Calculator useful.