How to Measure the ST Segment of an ECG



To determine the ST elevation, it is important to know where to measure the ST segment from. For that, you need to find the J point. If you follow the QRS complex on your ECG, you will see that they are usually sharp-pointed. If you go down with the Q wave, up with the R wave, down the S wave and follow the S wave back to the baseline, it will usually pass the baseline. The moment that line goes horizontal, that is where your J point is. You need to find the J point and then measure the distance between the baseline and the J point. If that distance is more than two little blocks in the precordial leads (in other words, two millimetres) - or more than one little block in the limb leads (in other words, one millimetre) - then we say the ST segment is elevated.
CPD time1m
First Published02 June 2019
Updated02 June 2019
29 June 2025
Learning Tools