ECG Boxes to Seconds Calculator
Convert ECG grid measurements to time intervals for accurate ECG interpretation
ECG Grid Conversion
Understanding ECG Grid
ECG paper is printed with a grid pattern that helps measure time intervals and amplitudes:
- Small Box: 1mm × 1mm = 0.04 seconds (horizontal) × 0.1 mV (vertical)
- Large Box: 5mm × 5mm = 0.2 seconds (horizontal) × 0.5 mV (vertical)
- Paper Speed: Standard is 25 mm/sec, but can vary (12.5, 50 mm/sec)
Conversion Details
Input Value:
Box Type:
Paper Speed:
Box Size:
Conversion Result:
Formula Used:
ECG Grid Reference
Small Box:
1mm × 1mm = 0.04 seconds × 0.1 mV
Large Box:
5mm × 5mm = 0.2 seconds × 0.5 mV
Standard Paper Speed:
25 mm/sec
Time per mm:
0.04 seconds (at 25 mm/sec)
Common ECG Intervals
PR Interval:
0.12-0.20 seconds (3-5 large boxes)
QRS Duration:
<0.12 seconds (<3 small boxes)
QT Interval:
0.36-0.44 seconds (9-11 small boxes)
RR Interval (60 BPM):
1.0 second (5 large boxes)
RR Interval (100 BPM):
0.6 seconds (3 large boxes)