120 140 Method Using the 6 Second Method 2 1 Draw two lines on the ECG trace. The first line should be near the left-hand side of the paper containing the ECG trace; the second line should be exactly 30 large squares subsequent to the first line. 30 large squares on an ECG trace represents exactly 6 seconds. 2 Count the number of QRS complexes between the two lines. As a reminder, the QRS complex is the tallest peak of each wave form that represents one heart beat. Tally up the total number of QRS complexes between your two lines and write down this number. 3 Multiply your answer by 10. Because 6 seconds x 10 = 60 seconds, multiplying your answer by 10 will give you the number of heart beats that have occurred in one minute (in other words, the "beats per minute," which is the standard measurement of heart rate). For example, if you count 8 beats in the 6 second period, then your heart rate calculation gives you 8 x 10 = 80 beats per minute. 4 Understand that this method is particularly effective for irregular heart rhythms. If the heart rate is regular, the first method of simply determining the distance between one QRS and the next can be very effective, because the distance between all the QRS complexes is presumably the same with a regular heart rate. On the other hand, with an irregular heart rate (where the QRS complexes are not at regular distances from one another), the 6 second method works better because it averages the distance between heart beats, giving a more accurate overall number.