Screen size calculator: width and height

How it works

Formula: Width = diagonal × 16 ÷ √(16² + 9²)

A screen's size is the length of its diagonal, in inches (1 inch = 2.54 cm). With the aspect ratio, say 16:9, the Pythagorean theorem gives the width and height: the diagonal of a 16 × 9 rectangle is √(16² + 9²) ≈ 18.36, and the rest is scaling. The sizes are for the visible screen, without the bezel or the stand.

Worked examples

• A 55 inch TV, 16:9

  121.8 × 68.5 cm of screen, with a diagonal of 139.7 cm.

• A 15.6 inch laptop, 16:9

  34.5 × 19.4 cm.

• 55 inches in 4:3 instead of 16:9

  The screen has 12% more area for the same diagonal.

Common mistakes

• Taking the diagonal for the width.

  A 55 inch screen is 121.8 cm wide, not 139.7 cm.

• Comparing screens of different ratios by diagonal alone.

  For the same diagonal, a 4:3 screen has 12% more area than a 16:9 one.

• Forgetting the bezel when checking if a TV fits a cabinet.

  The tool gives the visible screen: add the bezel from the maker's specs.

What the calculation leaves out

• Sizes of the visible screen, without bezel or stand: check the maker's specs for the full size.
• Screens with rounded corners or a notch are treated as rectangles.

Sizes of common 16:9 screens

Frequently asked questions