Corrected QT Interval
Calculates the heart-rate-corrected QT interval using Bazett, Fridericia, Framingham and Hodges formulas.
Measurement guidance
Enter the manually measured QT interval from the beginning of the QRS complex to the end of the T wave. When rhythm is irregular, assessment across several representative beats may be necessary.
ECG variables
Enter QT and heart rate
Reference sex category
Used only for the displayed prolonged-QT reference threshold. It does not alter the QTc calculation.
Primary displayed formula
All formulas are calculated. Select which result should be emphasized and interpreted.
Formula comparison
Important clinical considerations
QTc formulas may produce substantially different results, particularly at very high or very low heart rates. Always document which correction formula was used.
In patients with bundle branch block, ventricular pacing or a wide QRS complex, conventional QTc may overestimate repolarization duration. Assessment of the JT interval or another wide-QRS correction method may be more appropriate.
A single automated ECG measurement should be manually reviewed before making diagnostic or treatment decisions.
References
Rautaharju PM, Surawicz B, Gettes LS, Bailey JJ, Childers R, Deal BJ, Gorgels A, Hancock EW, Josephson M, Kligfield P, Kors JA, Macfarlane P, Mason JW, Mirvis DM, Okin P, Pahlm O, van Herpen G, Wagner GS, Wellens H; American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; American College of Cardiology Foundation; Heart Rhythm Society. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part IV: the ST segment, T and U waves, and the QT interval: a scientific statement from the American Heart Association Electrocardiography and Arrhythmias Committee, Council on Clinical Cardiology; the American College of Cardiology Foundation; and the Heart Rhythm Society: endorsed by the International Society for Computerized Electrocardiology. Circulation. 2009 Mar 17;119(10):e241-50. doi: 10.1161/CIRCULATIONAHA.108.191096. Epub 2009 Feb 19. PMID: 19228821.
Sagie A, Larson MG, Goldberg RJ, Bengtson JR, Levy D. An improved method for adjusting the QT interval for heart rate (the Framingham Heart Study). Am J Cardiol. 1992 Sep 15;70(7):797-801. doi: 10.1016/0002-9149(92)90562-d. PMID: 1519533.
This calculator provides clinical decision support and does not replace manual ECG interpretation, assessment of symptoms, medication review, electrolyte evaluation or specialist judgment.