ECG Heart Rate
Select your preferred method and enter the measured value. The calculator returns heart rate in beats per minute (bpm).
1500 rule – divide 1500 by the number of small boxes between R waves.
How to Use This Calculator
Choose a method
Select the approach that matches your ECG measurement (small boxes, large boxes, RR interval, or 6-second strip).
Measure accurately
Count boxes between R waves or measure RR interval duration. For irregular rhythms, average several intervals.
Review the rate
Interpret the calculated rate in clinical context (sinus bradycardia, tachycardia, atrial fibrillation, etc.).
Formula
1500 rule: HR = 1500 ÷ small boxes between R waves
300 rule: HR = 300 ÷ large boxes between R waves
RR interval: HR = 60 ÷ RR seconds
6-second strip: HR = (# of QRS in 6 s) × 10
Full Description
ECG heart rate estimation relies on the relationship between paper speed and time. The 1500 and 300 rules provide quick calculations for regular rhythms, while the 6-second method works well for irregular rhythms. RR interval measurement gives precise results, particularly with digital ECG systems that align calipers to the waveform.
Frequently Asked Questions
Which method is best for atrial fibrillation?
Use the 6-second strip or average of several RR intervals to account for beat-to-beat variability.
What if paper speed differs from 25 mm/s?
Adjust calculations accordingly. For example, at 50 mm/s, divide 3000 by small boxes (instead of 1500).
Does QT correction use the same interval?
QT correction (QTc) uses RR interval duration, often calculated via Bazett (QT ÷ √RR) or Fridericia formulas.
Can computerized ECG rates be inaccurate?
Automated measurements can misread arrhythmias. Manual verification using these methods is essential when results look incongruent.