QTc Calculator (Corrected QT Interval)
Calculate corrected QT interval using Bazett, Fridericia, or Framingham formulas.
Commas allowed (e.g. 1,200).
Educational use only. Always interpret QT/QTc with ECG quality, symptoms, electrolytes, and local protocols.
How it works
The QT interval varies with heart rate. QTc formulas adjust QT to estimate what it would be at a standard heart rate. This helps compare QT values between patients and across time.
The calculator first converts heart rate (HR) to RR interval in seconds using RR = 60 / HR, then applies the selected correction formula.
Formulas
QT is in milliseconds; RR is in seconds (RR = 60 / HR).
Worked examples
Example 1: QT 400 ms, HR 75 bpm — Bazett QTc
Example 2: QT 360 ms, HR 120 bpm — Bazett QTc
Clinical safety note: QTc thresholds depend on sex, rhythm, measurement method, and clinical context. A QTc >500 ms is commonly considered higher risk, especially with QT-prolonging medications or electrolyte abnormalities. Follow local protocols and escalate if the patient is unstable.
Related calculators
Frequently asked questions
Clinical reminder: Always follow local protocols and consult medication information sheets. These examples are for calculation practice only.
References & Sources
These resources provide clinical context for QT/QTc interpretation and torsades risk.
Clinical guidance & risk
AHA Scientific Statement — Prevention of torsade de pointes in hospital settings
GuidanceCirculation
Clinical guidance on risk factors, monitoring, and prevention strategies for torsades de pointes.
AHA/ACCF/HRS — ECG standardization & interpretation
ConsensusJ Am Coll Cardiol
Recommendations on ECG interpretation standards, including QT/QTc considerations.