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Category Medicine & Tests

Paper Speed:

Count small squares (1mm) between two R waves.

Small Squares:

Count large squares (5mm) between two R waves.

Large Squares:

Count total QRS complexes in a 6-second strip (30 large boxes).

Complex Count:

⚠️ Use this method for irregular rhythms (Afib).

-- BPM

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About

In emergency medicine and cardiology, quickly determining heart rate from an ECG strip is a fundamental skill. While automated machines provide readings, artifacts often cause errors, necessitating manual verification. This tool offers the three standard calculation methods used by paramedics and nurses.

The 1500 Method is the most accurate for regular rhythms, using the count of small millimeter boxes between R-waves. The 300 Method is a quick approximation using large 5mm boxes. The 6-Second Method is the only valid option for irregular rhythms like Atrial Fibrillation, where the R-R interval varies constantly.

Formulas

Standard paper speed is 25 mm/s. Formulas adapt if speed is changed to 50 mm/s.

{

Rate₁₅₀₀ = 1500n_small (Regular Rhythm)Rate₃₀₀ = 300n_large (Regular Rhythm)Rate_6s = count_R × 10 (Irregular Rhythm)

Reference Data

ECG Component	Normal Duration (sec)	Small Boxes (at 25mm/s)
P Wave	0.08 - 0.10	2 - 2.5
PR Interval	0.12 - 0.20	3 - 5
QRS Complex	0.06 - 0.10	1.5 - 2.5
QT Interval	0.36 - 0.44	9 - 11
Small Box	0.04	1
Large Box	0.20	5

Frequently Asked Questions

Use the 6-Second Method strictly for irregular rhythms (e.g., Atrial Fibrillation, PVCs). The 1500 and 300 methods assume a constant distance between heartbeats (R-R interval) and will give false results if the rhythm is irregular.

This is a memorization mnemonic for the 300 Method. If the R-wave falls on a heavy line, the next heavy lines represent rates of 300, 150, 100, 75, 60, 50. It allows for instant visual estimation without calculation.

Yes. Standard speed is 25mm/s. If the paper speed is 50mm/s (often used for pediatric detail), the calibration changes: 1500 becomes 3000, and 300 becomes 600.