The home office journal / Practical decisions

Monitor size calculator: diagonal into desk space

Estimate a screen rectangle, compare two displays and make room for the complete stand.

By Office Home Supply editorial · Updated 2026-10-10 · 2 minute read

What the calculator measures

A diagonal is one line across the visible panel. It does not describe the width of a monitor, the depth of its stand or the space you need to work in front of it. This calculator uses the diagonal and aspect ratio you supply to estimate the visible rectangle. The calculation is pure geometry: width equals diagonal times the horizontal ratio divided by the square root of the sum of the two squared ratio values. Height uses the vertical ratio in the same way. Inches convert to centimeters by multiplying by 2.54.

Use the result as a planning outline

Enter the diagonal stated for your screen and its actual aspect ratio. Use the result to draw a rough panel outline on cardboard. Add the manufacturer's complete outer dimensions and stand footprint before deciding whether the monitor fits. A portable display with a 16:10 shape has a different rectangle from a 16:9 screen at the same diagonal. Neither calculation includes the thickness of the bezel, which is why the complete product measurements still take priority.

A useful comparison for a small desk

The LG 24MR400-B and 27MR400-B records both identify Full HD IPS models with a 100Hz refresh capability, but their diagonals differ. Dell U2724D identifies a 27-inch QHD panel with a 120Hz capability. The larger rectangle and the higher resolution are separate decisions. A 27-inch Full HD screen does not provide more pixels than a 24-inch Full HD model; a different text scale or physical viewing arrangement may still suit your task. We have not tested text clarity or panel quality for these screens.

Two screens need more than twice a number

For a side-by-side plan, add both outer widths and a small working allowance for their angle and gap. Check the total stand area, or the support limits of a chosen arm. Place the cardboard outlines where the screens would sit and move the keyboard and mouse into their intended positions. The calculator does not establish viewing comfort, mounting compatibility or a safe furniture load. Keep those checks on a separate list, then save the finished plan with the exact model codes so a similar-looking suffix does not undo your measurements.

Sources & further reading

• LG 24MR400-B 24-inch FHD Monitor — official product information
• LG 27MR400-B 27-inch FHD Monitor — official product information
• Dell UltraSharp U2724D 27-inch Monitor — official product information

Original planning analysis based on the cited specifications. We do not claim hands-on testing. Confirm manufacturer compatibility and follow the supplied instructions.