Cardiovascular

Corrected QT interval (QTc)

Show Bazett and Fridericia heart-rate corrections from a measured QT and RR interval.

Intended population: Regular rhythm with narrow QRS and manually verified QT measurement; RR must be in seconds.

Bazett and Fridericia have rate-dependent error, especially at high or low rates. Verify QT end points on the ECG. Wide QRS, pacing or irregular rhythms require a more specific assessment; neither number alone diagnoses long-QT syndrome or selects therapy.

Measured QT interval (ms)

RR interval (seconds)

Rhythm and QRS suitability

Sources and scoring references

AHA/ACCF/HRS ECG standardization statement, part IV (2009) ↗

Implementation references reviewed October 28, 2026. Verify applicability and unusual or treatment-changing results against the linked references and local guidance.