Irregular Heart Rate ECG Calculator (6-Second Method)
Clinical Note: For irregular rhythms like Atrial Fibrillation, the standard "300-150-100" or "1500" methods are inaccurate. The 6-second method is the gold standard for calculating a mean heart rate in irregular rhythms.
Count every R-wave peak visible in your strip.
6 Seconds (Standard – 30 large boxes)
10 Seconds (Full Lead II strip – 50 large boxes)
3 Seconds (15 large boxes)
Standard ECG paper at 25mm/sec: 5 large boxes = 1 second.
Estimated Mean Heart Rate:
0
BPM
How to Calculate Heart Rate from an Irregular ECG
When an ECG rhythm is irregular (the distance between R-waves varies), you cannot use a single interval to determine the rate. Instead, you must calculate an average (mean) rate over a set period of time.
The 6-Second Rule Steps:
- Identify a 6-second strip: On standard ECG paper (25mm/sec), one large box is 0.2 seconds. Therefore, 30 large boxes equal 6 seconds.
- Count the R-waves: Count the number of QRS complexes within those 30 large boxes.
- The Math: Multiply the number of complexes by 10 (since 6 seconds × 10 = 60 seconds).
Realistic Example:
Imagine a patient with Atrial Fibrillation. You look at a 6-second strip (30 large boxes) and count 8 R-waves.
Calculation: 8 complexes × 10 = 80 BPM.
| Category | Rate (BPM) |
|---|---|
| Bradycardia | Below 60 |
| Normal Range | 60 – 100 |
| Tachycardia | Above 100 |