📈 QTc Calculator (Bazett & Fridericia)
Calculate the heart-rate–corrected QT interval (QTc) using both Bazett and Fridericia formulas.
Bazett over-corrects at fast and under-corrects at slow heart rates.
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When to use
Screen for QT prolongation and torsades risk before or during QT-prolonging therapy.
How it works
Bazett QTc = QT/√RR; Fridericia QTc = QT/∛RR (RR in seconds = 60/HR). Prolonged: > 450 ms (men) / > 470 ms (women); > 500 ms high risk.
Key points
- Bazett over-corrects at fast and under-corrects at slow heart rates.
- Fridericia is preferred outside 60–100 bpm.
- Wide QRS inflates QT — interpret with care.
References
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| QT interval | 400 ms |
|---|---|
| Heart rate | 75 bpm |
| Sex | Male |
→QTc (Bazett)447ms
- QTc (Fridericia)：431 ms
- Prolonged if：> 450 ms (male); > 500 ms = high torsades risk
Frequently asked questions
- What is QTc Calculator (Bazett & Fridericia)?
- Calculate the heart-rate–corrected QT interval (QTc) using both Bazett and Fridericia formulas.
- How is QTc Calculator (Bazett & Fridericia) calculated? What is the core formula?
- Bazett QTc = QT/√RR; Fridericia QTc = QT/∛RR (RR in seconds = 60/HR). Prolonged: > 450 ms (men) / > 470 ms (women); > 500 ms high risk.
- When is QTc Calculator (Bazett & Fridericia) used?
- Screen for QT prolongation and torsades risk before or during QT-prolonging therapy.
- What are the key clinical points for QTc Calculator (Bazett & Fridericia)?
- Bazett over-corrects at fast and under-corrects at slow heart rates. Fridericia is preferred outside 60–100 bpm. Wide QRS inflates QT — interpret with care.
- What are the limits and cautions when using QTc Calculator (Bazett & Fridericia)?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- How is QTc Calculator (Bazett & Fridericia) calculated in practice? Can you show a worked example?
- Inputs: QT interval 400 ms, Heart rate 75 bpm, Sex Male → Result: QTc (Bazett) 447 ms（QTc (Fridericia): 431 ms, Prolonged if: > 450 ms (male); > 500 ms = high torsades risk）