Screen-dimension calculator
Work out a screen's actual width and height from its diagonal size and aspect ratio — useful for checking whether it will physically fit a space before buying.
Result
Width
Height
How to use this calculator
- Enter the screen's diagonal size, as quoted in the spec sheet.
- Choose its aspect ratio.
- Read the actual width and height.
Assumptions
- Assumes the screen is a perfect rectangle at exactly the stated aspect ratio.
Technical details: what the fields mean
- Screen diagonal
diagonalInches - Diagonal screen size, as usually quoted in product listings (e.g. '55-inch TV').
- Aspect ratio
aspectRatio - The screen's width-to-height ratio — 16:9 is standard for most modern TVs and monitors, 21:9 for ultrawide monitors, 4:3 for older screens.
Methodology
Height = diagonal ÷ √(ratio² + 1). Width = height × ratio — derived from the Pythagorean relationship between width, height and diagonal.
Worked example
55-inch, 16:9 screen
Inputs: diagonalInches=55, aspectRatio=16:9
Result: 47.94in × 26.97in
Practical guidance
- Measure the actual space (shelf, wall mount, cabinet) using the calculated width and height, not just the diagonal figure, before buying a screen.
Common mistakes
- Assuming the diagonal size alone tells you whether a screen fits a space — two screens with the same diagonal but different aspect ratios have different actual widths and heights.
FAQs
How wide is a 55-inch TV?
About 47.9 inches wide and 27.0 inches tall, assuming the standard 16:9 aspect ratio.