A diagonal is not the width
For a flat rectangular panel with diagonal D and aspect ratio a:b, the panel width is D × a ÷ √(a² + b²). The height is D × b ÷ √(a² + b²). Use the same unit throughout. This is geometry; it does not depend on a particular brand.
For a 27-inch 16:9 panel, the result is approximately 23.53 inches wide and 13.24 inches tall. The housing and bezel add to those dimensions. A stand adds a separate footprint below the display.
Compare like with like
A 24-inch 16:9 panel is approximately 20.92 inches wide. The calculated difference from a 27-inch 16:9 panel is about 2.61 inches. Two displays magnify that difference across a narrow desk.
Aspect ratio changes the answer. For a 34-inch panel described by an exact 21:9 ratio, the estimate is about 31.25 inches wide. Marketing labels sometimes round aspect ratios, and curved housings require their own published dimensions. Treat calculated values as early planning estimates.
Use three separate specifications
For horizontal space, use the monitor housing's width. For desk surface occupation, use the assembled stand's footprint. For an arm, use the monitor weight without the stand plus mounting compatibility. None of these can be reliably inferred from the diagonal alone.
The calculator lets you supply an allowance for the bezel and housing. That allowance is a guess until you replace it with a manufacturer's measurement. It is useful for comparing layouts, but a close result should always trigger a check of the exact model.
About this guide
Worked examples are illustrative calculations, not measurements from product testing. Follow the instructions for your exact equipment. Read our research and correction policy.