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

The duration of a big box on ECG readings is accurately represented by 0.20 seconds. In standard ECG paper, each large box is subdivided into smaller boxes, with each small box measuring 0.04 seconds. Since there are five small boxes in a big box (5 x 0.04 seconds), this sums up to a total of 0.20 seconds for one big box. Understanding this measurement is essential in interpreting the timing of the electrical activity of the heart as reflected on the ECG, including assessing heart rate, rhythm, and potentially identifying abnormalities.