QTc Calculator
Calculate corrected QT interval to assess risk of arrhythmias. Includes Bazett and Fridericia formulas.
ECG Data
ms
Measured QT interval from ECG (in milliseconds). Measure from start of QRS to end of T wave. Best measured in leads II or V5-V6. Use the lead with the longest QT.
bpm
Heart rate at time of ECG. Calculated RR interval: {rrInterval.toFixed(3)} seconds. QT correction accounts for heart rate effects on QT.
Why sex matters: Females have longer normal QTc values than males. Upper normal limits differ: 450ms (male), 470ms (female).
QTc (Bazett)
— ms
Enter ECG data
QTc (Fridericia)
— ms
More accurate at extreme heart rates
Risk Assessment
High Risk (TdP)
Reference Ranges
| Category | Male | Female | Action |
|---|---|---|---|
| Normal | <450 ms | <470 ms | No action |
| Borderline | 450-470 ms | 470-480 ms | Review meds, electrolytes |
| Prolonged | >470 ms | >480 ms | Cardiology consult |
| High Risk | >500 ms | Discontinue offending drugs, monitor | |
The Formulas
Bazett Formula
QTc = QT / √RR
= 400 / √0.833 = ms
Fridericia Formula
QTc = QT / ∛RR
= 400 / ∛0.833 = ms
RR interval = 60 / Heart Rate = 60 / 72 = 0.833 seconds
Frequently Asked Questions