ECG Heart Rate Calculator
Work out heart rate from an ECG strip. Enter the number of boxes between two R waves — large boxes for the quick 300 method, small boxes for the precise 1500 method.
How to calculate heart rate on an ECG
- 300 method (regular rhythm): heart rate = 300 ÷ large boxes between two R waves.
- 1500 method (precise): heart rate = 1500 ÷ small boxes between two R waves.
- 6-second method (irregular): count QRS complexes in a 6-second strip and multiply by 10.
| Large boxes | Rate |
|---|---|
| 1 | 300 |
| 2 | 150 |
| 3 | 100 |
| 4 | 75 |
| 5 | 60 |
| 6 | 50 |
Learn the method in the ECG interpretation guide.
Frequently asked questions
How do you calculate heart rate on an ECG?
For a regular rhythm, divide 300 by the number of large boxes between two R waves; for more precision divide 1500 by the number of small boxes. For an irregular rhythm, count QRS complexes in a 6-second strip and multiply by 10.
What is the 300 method?
A quick way to read heart rate: 300 ÷ the number of large boxes between two R waves, giving the sequence 300, 150, 100, 75, 60, 50.
How do you find heart rate for an irregular rhythm?
Count the QRS complexes in a 6-second strip and multiply by 10.
Educational tool. These calculators are for study and RCIS exam preparation only — not for clinical decision-making or patient dosing. Always follow institutional protocols and verify with a qualified clinician.