How many millivolts does one small box (1mm) on an ECG represent?

In standard electrocardiography, one small box on the ECG paper, which measures 1 mm in height, corresponds to 0.1 millivolts (mV). This scaling is crucial for accurately interpreting the amplitude of the electrical signals generated by the heart. Each small box represents a measured increment, and if you know the scale, you can quantify the electrical activity in a more meaningful way, assisting in diagnosis and monitoring of cardiac conditions.

Understanding this basic metric is essential for paramedics and healthcare professionals in assessing heart conditions. Recognizing that a small box indicates 0.1 mV helps in calculating larger waveforms, as five small boxes make up one large box, equating to 0.5 mV, and further facilitating the interpretation of various patterns observed in an ECG.