QTc Calculator
QTc = QT ÷ √RR (Bazett), with RR = 60/HR. Click any i for detail.
ECG sketch
QT (ms)
i
QT
QT interval in milliseconds from the tracing or machine. |
|
|---|---|
Heart rate (bpm)
i
HR
Beats per minute. RR = 60 / HR seconds. |
How to use this calculator
- Enter QT in ms.
- Enter heart rate.
- Read Bazett on the headline and Fridericia in the breakdown.
- Machine QTc may already be corrected — don’t double-correct.
Results explained
RR (s) = 60/HR. Bazett: QT / √RR. Fridericia: QT / RR^(1/3). High or low HR makes Bazett less trustworthy — that’s why Fridericia is shown too.
Quick reference: QTc
At 60 bpm, RR = 1 s, so QTc equals QT.
| Item | Detail |
|---|---|
| Bazett | QT / √RR |
| Fridericia | QT / RR^(1/3) |
| 60 bpm | QTc = QT |
| Clinical cutoffs | Not printed — they are context-specific |
Lead choice and measurement technique matter more than this arithmetic.
How the estimate is built
QTcB = QT / sqrt(60/HR). QTcF = QT / (60/HR)^(1/3).
Example scenario
QT 400 ms at 70 bpm → Bazett about 432 ms.
FAQ
Which formula do hospitals use?
Varies. We show two common ones.
QT in squares?
Convert paper speed to ms first.
Meds and electrolytes?
Outside this calculator.