Standard ECG paper runs at 25 mm/s: each small box is 1 mm (0.04 s) and each large box is 5 mm (0.2 s). The box methods work only for regular rhythms; for irregular rhythms such as atrial fibrillation use the 6-second method.
How to use the ECG Heart Rate Calculator
- Method
- Paper speed
- Count
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose a method, the paper speed, and count either boxes between two consecutive R waves or QRS complexes in a 6-second strip.
Inputs explained
| Field | What to enter |
|---|---|
| Method | Choose one: Large boxes between R waves (300 method), Small boxes between R waves (1500 method), QRS complexes in 6 seconds |
| Paper speed | Choose one: 25 mm/s, 50 mm/s |
| Count | A number |
Example values
How the main result changes when Count changes and everything else stays at the example values above:
| Count | Heart rate (bpm) |
|---|---|
| 10 | 150 |
| 15 | 100 |
| 20 | 75 |
| 25 | 60 |
| 30 | 50 |
| 40 | 38 |
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
At 25 mm/s: HR = 300 ÷ large boxes between R waves = 1500 ÷ small boxes
6-second method: HR = QRS complexes in 6 s × 10
At 50 mm/s use 600 and 3000
Worked example
Inputs — Method: Small boxes between R waves (1500 method); Paper speed: 25 mm/s; Count: 20.
Results — Heart rate = 75 bpm; RR interval = 800 ms.
Key terms
- RR interval
- Time between two consecutive heartbeats on the ECG.
Frequently asked questions
What is a normal resting heart rate?
60–100 bpm in adults.
Which method is most accurate?
The 1500 method for regular rhythms; the 6-second method for irregular ones.
What if the paper speed is 50 mm/s?
Each box represents half the time, so the constants double.