Method 1
300 divided by number of big squares in R-R interval (1)
- Count the number of large squares present between R waves R-R interval
- Divide 300 by this number to calculate the heart rate
- The first method of calculating the heart rate doesn’t work when the R-R interval differs significantly throughout the ECG and therefore another method is required
e.g. 4 large squares in an R-R interval: 300/4 = 75 beats per minute
Method 2
Number of QRS complexes on rhythm strip x 6 (1)
- Count the number of complexes on the rhythm strip (each rhythm strip is 10 seconds long)
- Multiply the number of complexes by 6 (giving you the average number of complexes in 1 minute)
e.g. 10 complexes on a rhythm strip X 6 = 60 beats per minute