Marian Stiehler

This is a translation of a German web site. Don’t be confused if you encounter poor wording. The presented data and the calculations are correct.

Please visit my new project about Short QT Syndrome!

Please note that the ESC has published new guidelines in 2022. Long QT guidelines are virtually unchanged. Short QT guidelines did change. The new guidelines are not yet included in this calculator, but you can find them on


ESC Guidelines 2015 (see below):

Comparison of QTcFri (highlighted in red) with distribution of QTcFri in the normal population (Vandenberk et al., 2016):

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.

Graphical representation of QT = 414 ms

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

Measuring the QT interval

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):

Further information:


ESC 2015, Mazzanti 2014, Gollob 2011, AHA 2009, FDA 2005, Schwartz 1993, Schwartz 1985

Distribution of QTc 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 QTc values in the normal population is unknown; there are, however, large scale studies.

The following is based on a study by Vandenberk et al., 2016 on 6,609 Europeans, aged 59.8±16.2 years. The recorded ECGs had heart rates of 68.8±10.6 beats per minute.


The distribution of Bazett values is shown in gray.

For women Vandenberk et. al. recorded a QTcFri interval of 417±25 ms.

For men they recorded a QTcFriinterval of 412±24 ms.

Assuming a normal Distribution, 20,000 measurements can be simulated. You can see clearly how rare long and short QT values are in the normal population:

QTc Calculator as an app for iPhone

There is a version of this QTc calculator for iPhone and iPad: nine 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:

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:

QTlc Sagie (Framingham Heart Study)

correction formula (for msec): \(\text{QTlc} = 1000 (\text{QT} + 0,154 (1 – \text{RR}))\)

published in 1992; 5.018 subjects

original publication:

QTc Hodges

correction formula: \(\text{QTc}_\text{H} = \text{QT} + 1,75 (\text{HR} -60)\)

published in 1983; 607 subjects

original publication (page 694, bottom):

QTc Rautaharju a

correction formula: \(\text{QTc}_\text{Mod} = \text{QT}(120 + \text{HR})/180\)

published 2014; 57,595 subjects

original publication: 

QTc Rautaharju b

correction formula men: \(\text{QTc}_\text{LogLin} = \text{QT} + 387 (1 - \text{RR}^{0,37})\)

correction formula women: \(\text{QTc}_\text{LogLin} = \text{QT} + 409 (1 - \text{RR}^{0,39})\)

published 2014; 57,595 subjects

original publication:

Conversion heart rate ↔ RR interval

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


You can use the images and information on this web site for free, for example in talks, at the university or even in publications. Please be fair and don’t offer your own QT calculator.

A short note or a link to this web site would be great–and you can always send me an email: [email protected].

Privacy / Liability

The calculations are performed locally in your browser. No data is being transmitted to the internet / a server. Your visit on this web site is not being tracked or analyzed. The connection to this web site is encrypted. This service is free of charge. Calculations and all information come without any liability.