Check the monitor model number on the back label or in the monitor menu
Search the model number online to find the listed screen size
Measure the visible screen diagonally from one corner to the opposite corner
Measure only the display area, not the bezel or frame
Use a ruler or tape measure and record the length in inches
Compare the measurement with standard monitor sizes
Check the product box, manual, or purchase receipt for the size
Look in your computer’s display settings or device information if the monitor is connected to a system that reports it