TV & Screen Size Calculator
Enter a screen's diagonal size and aspect ratio to calculate its actual width and height — useful for checking whether a TV or monitor will physically fit a space before buying.
How the TV & Screen Size formula works
Using the Pythagorean theorem with the aspect ratio's proportions:
Width = Diagonal × (Ratio width / √(Ratio width² + Ratio height²)) Height = Diagonal × (Ratio height / √(Ratio width² + Ratio height²))
Step-by-step calculation
- Calculate the hypotenuse factor from the aspect ratio's width and height values.
- Multiply the diagonal by the ratio's width component divided by that factor to get actual width.
- Multiply the diagonal by the ratio's height component divided by that factor to get actual height.
Worked example
A 55-inch TV at a standard 16:9 aspect ratio: factor = √(16²+9²) = √337 ≈ 18.36. Width = 55 × (16/18.36) ≈ 47.9 in. Height = 55 × (9/18.36) ≈ 27.0 in.
Frequently asked questions
Is TV size always measured diagonally?
Yes — screen sizes for TVs, monitors, and phones are conventionally measured corner to corner (diagonally), which is why two screens with the same stated size but different aspect ratios can have different actual widths and heights.
What's the standard aspect ratio for TVs?
16:9 is the standard for nearly all modern TVs and most monitors. Older TVs and some content used 4:3, and ultrawide monitors commonly use 21:9.