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ECG Boxes to Seconds Calculator
Convert electrocardiogram grid boxes into time in seconds (Standard 25 mm/s speed)
ECG Timing Standard: At standard ECG paper speed of 25 mm/s, 1 small square box = 0.04 seconds (40 ms) and 1 large square box (5 small boxes) = 0.20 seconds (200 ms). Enter boxes below.
ECG Grid Input
Calculation Results
⚠️ Not medical advice. For clinical nursing, medical education, and ECG reference only. Electrocardiogram interpretations and cardiac interval measurements must be verified by a qualified physician or cardiologist.