Health

ECG Boxes to Seconds Calculator

Convert ECG grid boxes to time intervals.

Large Boxes (5mm each)

Small Boxes (1mm each)

Paper Speed

Time—

Milliseconds—

Total mm—

At 25 mm/sec: 1 small box = 0.04s (40ms), 1 large box = 0.20s (200ms).
At 50 mm/sec: 1 small box = 0.02s, 1 large box = 0.10s.