QTc Calculator — Corrected QT Interval
Enter the QT interval from an ECG and the heart rate. The calculator applies your chosen correction formula (Bazett, Fridericia, Framingham or Hodges) to produce the rate-corrected QTc and flags prolongation by sex-specific thresholds.
ms
bpm
Пол
Correction formula
Borderline prolonged QTc — clinical assessment advised
- 1
RR interval
(60 ÷ 75) × 1000 = 800Time between heartbeats in milliseconds. - 2
√RR (seconds)
√0,8 = 0,8944 - 3
Bazett QTc
(0,4 ÷ 0,8944) × 1000 = 447,2
Как работи този калкулатор?
QTc corrects the raw QT interval for heart rate so it can be compared across conditions. Bazett: QTc = QT/√RR; Fridericia: QTc = QT/∛RR (RR and QT in seconds). Normal QTc < 440 ms (men) or < 460 ms (women); ≥ 500 ms is prolonged with torsades de pointes risk. ECG interpretation requires a clinician.
Формула
How this is calculated
The QT interval on an ECG represents ventricular depolarisation and repolarisation. Because QT naturally shortens at faster heart rates, comparing raw QT values between patients (or in the same patient at different heart rates) requires a rate correction to produce QTc. The four formulae implemented here all achieve this by normalising the measured QT to an equivalent value at 60 bpm (RR = 1 s).
Bazett's formula (QTc = QT ÷ √RR) is the oldest and most widely quoted but overcorrects at very fast or slow heart rates. Fridericia's cube-root correction (QTc = QT ÷ ∛RR) performs better across a wider HR range and is increasingly preferred in drug-safety studies. Framingham's linear correction (QTc = QT + 0.154 × (1 − RR)) and Hodges' rate-specific linear formula tend to agree with Fridericia at normal rates. All four are shown side by side so you can compare.
Prolongation thresholds: a QTc ≥ 440 ms in men or ≥ 460 ms in women is conventionally considered borderline; ≥ 500 ms in either sex indicates significant prolongation with increased risk of torsades de pointes, a life-threatening ventricular arrhythmia. These thresholds are approximate — the clinical significance always depends on symptoms, medications, electrolytes, congenital channelopathies, and the specific formula used. This tool is for educational screening only; ECG interpretation must be confirmed by a clinician.
Често задавани въпроси
Bazett is the most recognised and is used in most automated ECG machines, making it the default for consistency. Fridericia is generally preferred for drug-safety studies and at extreme heart rates. If a cardiologist or protocol specifies a formula, use that one.
A QTc ≥ 500 ms carries a meaningful risk of torsades de pointes regardless of sex. Many drug safety agencies use 500 ms as a hard threshold and 60 ms prolongation from baseline as a secondary flag. Consult a clinician for any QTc ≥ 460 ms in men or ≥ 480 ms in women.
Many factors prolong QT: medications (antiarrhythmics, antibiotics, antipsychotics, antihistamines), electrolyte disturbances (hypokalaemia, hypomagnesaemia, hypocalcaemia), hypothyroidism, liver disease, and inherited ion-channel mutations (long QT syndrome). A short QT may indicate hypercalcaemia or short-QT syndrome.
Известен също като
TG we-Calculate Editorial Team. (2026). QTc Calculator — Corrected QT Interval [Online calculator]. TG we-Calculate. https://we-calculate.com/bg/calculator/qtc-calculator
TG we-Calculate Editorial Team. "QTc Calculator — Corrected QT Interval." TG we-Calculate. 2026. https://we-calculate.com/bg/calculator/qtc-calculator.
TG we-Calculate Editorial Team, "QTc Calculator — Corrected QT Interval," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/bg/calculator/qtc-calculator
@misc{wecalculate_qtc_calculator, title = {QTc Calculator — Corrected QT Interval}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/bg/calculator/qtc-calculator}}, year = {2026}, note = {TG we-Calculate} }
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