What this monitor size calculator does
This monitor size calculator estimates the diagonal screen size of a monitor using its visible width and height. Monitor size is typically advertised by the diagonal measurement, not by the horizontal or vertical dimensions alone. By entering the screen width and height in inches, you can quickly calculate the true diagonal size using the Pythagorean theorem. This is useful when comparing displays, checking product specs, or confirming the size of an existing monitor.
How to use it
Measure the visible display area from left to right for width and from top to bottom for height, excluding bezels or the outer frame. Enter both values in inches into the fields above, then click the calculate button. The tool will instantly show the monitor’s diagonal size in inches. For best accuracy, use a tape measure and round only at the end. If you know the dimensions in another unit, convert them to inches first before using the calculator.
Practical examples
If a screen measures about 20.9 inches wide and 11.8 inches tall, the diagonal is roughly 24 inches. A display measuring around 23.5 inches by 13.2 inches is about 27 inches diagonally. This can help when buying a replacement monitor, mounting multiple screens, or checking whether a listed size matches the actual panel. It is also handy for office setups, gaming desks, and home workstations where exact monitor dimensions matter for fit and viewing comfort.