What is the duration of a little box on ECG readings in seconds?

In an electrocardiogram (ECG) reading, each small square (or "little box") on the grid represents a specific duration of time. The standard duration of a little box is 0.04 seconds. This is calculated based on the paper speed of the ECG, which is typically set at 25 millimeters per second. Since the little box measures 1 millimeter, it corresponds to a time interval of 0.04 seconds (1 mm/25 mm per second).

This standard measurement is crucial for interpreting heart rhythms, calculating heart rates, and identifying abnormalities in the ECG waveform. Understanding this time duration helps healthcare professionals accurately assess cardiac function and guide clinical decisions.