Corrected QT (Framingham) Calculator

How it is calculated

The tool first turns heart rate into the RR interval, the time between beats: RR (s) = 60 ÷ HR, with HR in beats per minute. It then applies the Framingham linear correction QTc = QT + 154 × (1 − RR), with QT in milliseconds and RR in seconds. At 60 bpm RR is exactly 1 s, so QTc equals the measured QT; a faster rate makes the correction positive and a slower rate makes it negative. QTc is rounded to whole ms and RR to two decimals. QT must be between 100 and 1000 ms and heart rate between 20 and 250 bpm; outside those limits the tool shows no result. It does not say what counts as a normal or prolonged QTc. It is educational only, and other formulas (Bazett, Fridericia) give different values.

Common mistakes

• Entering QT in seconds (0.4) instead of milliseconds (400). The tool needs at least 100 ms, so it shows no result rather than a wrong value.
• Entering the RR interval in the heart-rate box. The heart-rate field wants beats per minute, not milliseconds between beats, and a value such as 800 is outside the accepted 20 to 250 range.
• Using an average heart rate for the whole recording while the QT was measured on a single beat. The correction should use the heart rate at the beat where QT was measured.
• Comparing a Framingham value against a Bazett cut-off. The formulas differ, mostly at fast or slow rates, so a threshold from one method should not be applied to another.
• Treating the output as a diagnosis. The tool only corrects a number; it does not judge whether the QTc is normal.