ECG Heart Rate Calculator
Standard clinical methods for R-R interval analysis.
How to Calculate Heart Rate on an ECG
Electrocardiogram (ECG) interpretation requires a systematic approach to determining the heart rate. Depending on whether the rhythm is regular or irregular, medical professionals use three primary methods.
1. The 1500 Method (Most Accurate for Regular Rhythms)
Since standard ECG paper moves at 25 mm/sec, there are 1,500 small boxes (1mm each) in one minute. To find the rate, count the number of small boxes between two consecutive R-waves (the R-R interval).
Formula: 1500 / Number of Small Boxes = Heart Rate (BPM)
2. The 300 Method (The Sequence Method)
This is a quick way to estimate rate using the large boxes (5mm each). There are 300 large boxes in one minute.
Formula: 300 / Number of Large Boxes = Heart Rate (BPM)
3. The 6-Second Strip Method (Best for Irregular Rhythms)
If the heart rate is irregular (like in Atrial Fibrillation), the previous methods are inaccurate. Instead, count the number of QRS complexes (R-waves) within a 6-second interval (usually marked by markers at the top of the paper) and multiply by 10.
Formula: Number of R-waves in 6 seconds x 10 = Heart Rate (BPM)
Clinical Interpretation Table
| BPM Range | Classification |
|---|---|
| Below 60 | Bradycardia |
| 60 – 100 | Normal Sinus Rhythm |
| Above 100 | Tachycardia |