QTc Calculator
Result
432ms
Normal
Bazett formula. Normal: men <440 ms, women <460 ms. Risk threshold: >500 ms.
How to use it
- 1
Measure QT manually. From start of QRS to end of T-wave. Use lead II or V5. Average 3–5 beats.
- 2
Select formula. Bazett is most common but overcorrects at high HRs. Fridericia is preferred by most guidelines. Framingham is a linear correction.
- 3
Interpret. QTc >500 ms: high torsades risk. Review all QT-prolonging drugs immediately.
When to use it
- Starting QT-prolonging drugs
- Antibiotics (azithromycin, moxifloxacin), antipsychotics, amiodarone, ondansetron, methadone, hydroxychloroquine.
- Hypokalaemia or hypomagnesaemia
- Electrolyte abnormalities potentiate QT prolongation. Correct K+ >4.0 and Mg²+ >1.0 mmol/L.
- Syncope evaluation
- Long QT syndrome (congenital or acquired) can cause torsades and VF presenting as syncope.
A reference for clinicians and students, not medical advice. A score supports a decision; it does not make one. Check every result against the patient in front of you and your local protocol.
At a glance
- Specialty
- Cardiology
- Inputs
- 3
- Type
- Formula
