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Comparison of the calculated QTc values with distribution of QTcBzt in the normal population (Funada et al., 2008):

Please enter values for heart rate or RR interval and QT interval.

QTc values are rounded to milliseconds.

Transgression of QTc limits is indicated by colors yellow and red, according to the ESC guidelines of 2015 – see below.

For formulae, see below.


Limits for Long/Short QT Syndrome

Unfortunately, the limits for Long and Short QT Syndrome are disputed. According to one of the most recent publications (ESC Guidelines, 2015):

  • Long QT Syndrome: ≥480 ms even if asymptomatic; ≥460 ms if symptomatic
  • Short QT Syndrome: ≤340 ms even if asysmptomatic; ≤360 ms if symptomatic or other factors

Distribution of QTcBzt in the normal population

Please be advised that this section presents data from a single study which has some limitations. Be careful.

The exact distribution of QTcBzt values in the normal population is unknown; there are, however, large scale studies.

The following representation is based on a study by Funada et al., 2008, with 10,984 Japanese subjects (50 % males):

In males, QTcBzt was 404 ± 25msec (gray).
In females, QTcBzt was 412 ± 24 msec (gray).


Graphical representation of QT = 408 ms

At a measured QT of 408 ms, QTc is the following depending on heart rate:


QTc Calculator as an app for iPhone

There is a version of this QTc calculator for iPhone and iPad: four correction formulas, graphical representation of results and a small knowledge base. more


Correction Formulae

QTc Bazett

correction formula: \(\text{QTc}_{\text{Bzt}} =\frac{\text{QT}}{\sqrt{\text{RR}}}\)

published in 1920; 39 subjects

original publication: https://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111/j.1542-474X.1997.tb00325.x

QTc Fridericia

Sometimes spelled “Fredericia”.

correction formula: \(\text{QTc}_{\text{Fri}} = \frac{\text{QT}}{\sqrt[3]{\text{RR}}}\)

published in 1920; 50 subjects

original publication: https://onlinelibrary.wiley.com/doi/abs/10.1111/j.0954-6820.1920.tb18266.x

QTlc Sagie (Framingham Heart Study)

correction formula (for msec): \(\text{QTlc} = 1000 (\text{QT} + 0.154 (1 – \text{RR}))\)

correction formula: \(\text{QTc}_\text{H} = \text{QT} + 1.75 (\text{HR} -60)\)

published in 1983; 607 subjects

original publication (page 694): http://www.onlinejacc.org/content/1/2_Part_2/577

Conversion heart rate ↔ RR interval

\(\text{RR} = \frac{60}{\text{HR}}\)


Privacy / Liability

This web site does not collect any personal data. The calculations are performed locally on your device. No data will be sent to a server. Your visit on this web site is not being monitored by the provider. The connection is encrypted. This service is free of charge. All information is supplied without liability and all obligation is excluded due to faulty, incomplete or outdated information.