Skip to content
ENExplore Calculators

Heart Rate From ECG Calculator

Work out heart rate from ecg instantly with clear inputs, formula shown and shareable results.

About Heart Rate From ECG Calculator

Turns the number of 1 mm ECG squares between consecutive R waves into a heart rate, using the recording paper speed.

Formula

Rate from R-R

R-R (s) = small squares / paper speed (mm/s); HR = 60 / R-R. At 25 mm/s this is the familiar 1500 / squares rule.

Worked example

With the default values below, Heart Rate From ECG Calculator returns Heart rate of 75. Change any input above and every figure here is recalculated in your browser.

Inputs used

Small squares between two R wavesaccepts 1–200
20
Paper speedone of 25 mm/s (standard), 50 mm/s
25 mm/s (standard)

Results

Heart rate
75 bpm
R-R interval
0.800 s
Rate band
Normal rate (60-100 bpm)

Step by step

  1. 1Values used
  2. 2Rate from R-R
  3. 3Heart rate= 75 bpm
  4. 4R-R interval= 0.800 s
  5. 5Rate band= Normal rate (60-100 bpm)

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Why 1500 divided by small squares?

At 25 mm/s each 1 mm square is 0.04 s, so 60 / (squares x 0.04) = 1500 / squares.

Does this work for irregular rhythms?

No. For an irregular rhythm count the QRS complexes over a 6-second strip and multiply by 10 instead.

Related Calculators

Heart Rate From ECG Calculator | Calcrivo