ECG Heart Rate (BPM) Calculator
Calculate Heart Rate from EKG Strips using the Square Method
25 mm/s (Standard)
50 mm/s
Small Squares (1500 Method)
Large Squares (300 Method)
Estimated Heart Rate:
—
BPM
How to Use ECG to Calculate Heart Rate
Electrocardiogram (ECG) strips are printed on standardized grid paper. To calculate the heart rate (beats per minute), you must measure the distance between two consecutive R-waves (the peak of the heartbeat), known as the R-R interval.
The Two Main Methods
- The 300 Method (Large Squares): Best for regular rhythms. Count the number of large 5mm squares between R-waves. Divide 300 by that number. (Example: 4 large squares = 300 / 4 = 75 BPM).
- The 1500 Method (Small Squares): Most accurate for regular rhythms. Count the number of small 1mm squares between R-waves. Divide 1500 by that number. (Example: 20 small squares = 1500 / 20 = 75 BPM).
Understanding ECG Grid Math
Standard ECG paper moves at 25 mm/second. This means:
- 1 small square = 1 mm = 0.04 seconds
- 1 large square = 5 mm = 0.20 seconds
- 1500 small squares = 60 seconds (1 minute)
- 300 large squares = 60 seconds (1 minute)
Interpretation Guidelines
- Normal: 60 – 100 BPM
- Bradycardia (Slow): Under 60 BPM
- Tachycardia (Fast): Over 100 BPM
Note: For irregular rhythms, clinicians usually use the 6-second strip method (counting R-waves in a 6-second window and multiplying by 10) for better accuracy.