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

Get it on Google Play English badge

Scan QR code for Apple iOS version

Notes on EP Calipers for Windows

There are 3 versions of EP Calipers for Windows available.

The first two versions are for individual users and can be used on a per user basis on multiple machines on which the user has an account. The third version is intended for IT administrators who work in hospitals or clinics. It allows the program to be installed on a per machine basis so that any user with an account on that machine can use the app. If you are uncertain what the implications of this difference are, it is recommended that you install one of the first two versions.

All versions are identical in function.  Updates to the program are free for all versions; however users with the Microsoft App Store version will receive automatic update notices, which is not (at present) possible via FastSpring.  Purchasers of the FastSpring versions of EP Calipers will be emailed a coupon for free updates when updates are available.

It is possible to run the FastSpring version on earlier versions of Windows (back to Vista SP2!); however,  it is necessary to download the Windows Universal CRT update.  Please read the instructions of the linked page carefully to set up your system.

EP Calipers for Windows Licensing

EP Calipers for Windows (Fastspring or Microsoft App Store versions) is licensed on a one copy per one user basis. EP Calipers for Windows Administrators is licensed on a one copy per machine (unlimited users) basis.


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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