EP Calipers

EP Calipers allows you to use electronic calipers to make measurements on images of ECGs or EP recordings.  Use time calipers to measure intervals or heart rate, amplitude calipers to measure voltage, and angle calipers for specialized uses such as evaluating Brugada Syndrome. See this post for more details.

EP Calipers is available for iPhone or iPad,  Android devices,  Mac, and Microsoft Windows™.

Get EP Calipers

Note on EP Calipers for Windows

A new version of EP Calipers for Windows, EP Calipers 3 is now available on the Microsoft Store. See this blog post for more information on this completely rewritten version of the app.

The original version, the version 2.x series, is still available and will be supported, but it is encouraged that new users obtain the new version and users of the original version are encouraged to upgrade.

EP Calipers for Windows is only available from the Microsoft Store. Users and institutions interested in obtaining the app outside of the Store or who want a multi-user license should contact support at EP Studios directly.


Add time, amplitude, or angle calipers
Time caliper before calibration
Measure a known interval to calibrate (e.g. 5 “boxes” at 25 mm/sec standard ECG speed which equals 1000 msec)
Caliper after calibration
Calipers maintain calibration with image zoom
Toggle between interval measurements and heart rate
Measure mean intervals and heart rates. Useful for irregular rhythms like atrial fibrillation.
Use calipers to measure the QT interval
Calculate the QTc using 4 different formulas
Using marching calipers to evaluate complex arrhythmias
Take photos of ECGs or load ECG images from your photo library. You can open PDF files with EP Calipers to analyze figures in published papers.

Other examples

Calculating QTc on a Windows PC
Transparent window on macOS Mojave
Measuring mean rate and interval on a Mac
Measuring mean rate and interval on a Mac
Making EP measurements on an iPad
Making EP measurements on an iPad
Marching calipers on the MacOS version
EP Calipers running on Microsoft Vista using the Universal CRT

YouTube videos

Note: some of these are a bit dated and lack some of the newer features, but they should give you a general idea of how to use the app on different platforms.

EP Calipers for Windows
(Note that this video does not demonstrate the transparent window mode)
EP Calipers on iPad
 Angle Calipers
New Features, including transparent window mode

Source code for iOS

Source code for Android

Source code for macOS

Source code for Windows


  1. ep calipers is useless on Mac you can not get the measurements in ms and most of the features are grayed out. It would have been nice to know this before purchasing.

  2. Do you have any validation data on this program to support it is fairly accurate and precise when making measurements for intervals compared to hand measurements with physical calipers?

    1. No, not formally. However, the calipers are just measuring screen distances in pixels and applying scaling factors using floating point arithmetic. The code is open source and on GitHub so it can be examined. Nevertheless, errors could occur particularly in photographed ECGs, where the ECG is not perpendicular to the camera or the photo is otherwise distorted.

      If you are considering using the program for research it would be important to compare hand and electronic measurements to validate the technique.

  3. Hello
    I bought the EP calipers app but it does not meet my expectations. I would like to request a refund.
    Thank you

    1. Hi Olga, sorry to hear that. I don’t handle refunds directly. You should contact wherever you bought it from (Apple App Store, Google Play, Microsoft Store or Fastspring).

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