ECG Heart Rate Calculator

How to Get Heart Rate from an ECG

Heart rate on an electrocardiogram equals the number of cardiac cycles per minute. On a regular rhythm, measure the R-R interval between two consecutive R-wave peaks, convert that distance to time using paper speed, then divide 60 seconds by that duration. Use the ECG Boxes to Seconds Calculator when you count grid boxes instead of millimeters, or the Target Heart Rate Calculator for exercise zones.

ECG Heart Rate Formula

First find R-R duration in seconds. If you measured millimeters, divide by paper speed (mm/s). If you counted boxes, multiply by the duration of one box at that speed. Then:

$$ \text{Heart Rate (BPM)} = \frac{60}{\text{R-R duration (s)}} $$

300 and 1500 Rules

Without a calculator, divide 300 by the number of large boxes or 1500 by the number of small boxes between R peaks at 25 mm/s paper speed. At 50 mm/s, use 600 and 3000 instead. These shortcuts match the full formula when the rhythm is regular.

6-Second Method for Irregular Rhythms

When R-R intervals vary, count R waves in a 6-second strip (30 large boxes at 25 mm/s) and multiply by 10 for an estimated rate. This tool assumes a regular rhythm and may be inaccurate during arrhythmia.

Normal Resting Values

Adults typically show 60 to 100 BPM at rest. Below 60 is bradycardia; above 100 is tachycardia. Pediatric ranges differ by age. Always interpret ECG findings in clinical context.