# ECG Heart Rate Calculator

URL: https://speedycalculator.com/calculators/health/ecg-heart-rate/
Last updated: 2026-10-30

> The ECG heart rate calculator works out the heart rate from an electrocardiogram strip with the 300 method (large boxes), the 1500 method (small boxes) or the 6-second method (QRS complexes counted in 6 seconds), at 25 or 50 mm/s paper speed.

## Inputs

- Method
- Paper speed
- Count

## Results

- Heart rate
- RR interval

## 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
```

## Explanation

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

FieldWhat to enterMethodChoose one: Large boxes between R waves (300 method), Small boxes between R waves (1500 method), QRS complexes in 6 secondsPaper speedChoose one: 25 mm/s, 50 mm/sCountA number

### Example values

How the main result changes when **Count** changes and everything else stays at the example values above:

CountHeart rate (bpm)10150151002075256030504038
*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.*

## 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.

## FAQ

**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.


## Sources

- [Life in the Fast Lane – ECG rate interpretation](https://litfl.com/ecg-rate-interpretation/)