ECG Heart Rate Calculator
Use this calculator to determine heart rate from an Electrocardiogram (ECG) strip. Choose the appropriate method based on the rhythm's regularity.
(For regular rhythms only. Count small squares between two consecutive R-waves.)
(For irregular rhythms. Count R-waves in a 30-large-square strip.)
Understanding Heart Rate Calculation from ECG
An Electrocardiogram (ECG or EKG) is a simple, non-invasive test that records the electrical activity of the heart. It's a fundamental tool in cardiology for diagnosing various heart conditions. One of the most basic yet crucial pieces of information derived from an ECG is the heart rate.
Why Calculate Heart Rate from ECG?
While a pulse can give a quick estimate, an ECG provides a precise measurement of the heart's electrical beats, which is essential for accurate diagnosis and monitoring. It helps identify bradycardia (slow heart rate), tachycardia (fast heart rate), and irregular rhythms (arrhythmias).
ECG Paper Basics
ECG paper is standardized. It moves at a speed of 25 mm/second. The paper is marked with a grid:
- Small squares: 1 mm x 1 mm. Each small square represents 0.04 seconds horizontally.
- Large squares: 5 mm x 5 mm (composed of 5×5 small squares). Each large square represents 0.20 seconds horizontally (5 x 0.04 seconds).
Methods for Calculating Heart Rate
1. The 1500 Method (For Regular Rhythms)
This is the most accurate method for calculating heart rate when the rhythm is regular (i.e., the R-R intervals are consistent). It leverages the precise timing of the small squares.
Formula: Heart Rate (bpm) = 1500 / Number of Small Squares between two consecutive R-waves
How to use:
- Identify two consecutive R-waves (the tall, sharp peaks on the ECG).
- Count the exact number of small squares between the beginning of one R-wave and the beginning of the next R-wave.
- Divide 1500 by this number.
Example: If there are 25 small squares between two R-waves:
Heart Rate = 1500 / 25 = 60 bpm
2. The 300 Method (For Regular Rhythms)
This is a quicker, less precise method for regular rhythms, often used for a rapid estimate.
Formula: Heart Rate (bpm) = 300 / Number of Large Squares between two consecutive R-waves
How to use:
- Identify an R-wave that falls on a thick line (start of a large square).
- Count the number of large squares until the next R-wave.
- Divide 300 by this number.
Example: If there are 4 large squares between two R-waves:
Heart Rate = 300 / 4 = 75 bpm
3. The 6-Second Method (For Irregular Rhythms)
This method is particularly useful for irregular rhythms where the R-R intervals vary significantly, making the 1500 or 300 methods unreliable.
Formula: Heart Rate (bpm) = Number of R-waves in a 6-second strip x 10
How to use:
- Locate a 6-second strip on the ECG. A 6-second strip typically spans 30 large squares (6 seconds / 0.20 seconds per large square = 30 large squares). Many ECGs have markings at the top indicating 3-second or 1-second intervals.
- Count the total number of R-waves within this 6-second segment.
- Multiply this count by 10 to get the heart rate in beats per minute.
Example: If you count 7 R-waves in a 6-second strip:
Heart Rate = 7 x 10 = 70 bpm
Using the Calculator
Our calculator simplifies these calculations. Select whether the rhythm is regular or irregular, then input the required value (either small squares for regular rhythm or R-waves in a 6-second strip for irregular rhythm) and click "Calculate Heart Rate" to get an instant result.