electronic magnification | OptoWiki Knowledge Base

describes, how much larger an image sensor is displayed on a monitor.

$ElectronicMagnification = \frac{MonitorSize}{SensorSize}$

May the diagonal of the sensor be 6mm (third inch) and the monitor diagonal be 50″ = 128cm = 1280mm
$ElectronicMagnification = \frac{MonitorSize}{SensorSize}= \frac{1280}{6}=213.33$

see also:
optical magnification
monitor magnification