Quick answer
Screen width = diagonal × aw ÷ √(aw² + ah²), and height uses ah. A 55 inch 16:9 screen is 47.94 × 26.96 in (121.8 × 68.5 cm), with an area of 1,292.6 in².
Enter the diagonal and the aspect ratio. The calculator returns width, height and area. Use this screen size calculator to check your own figures.
Related tools: 16:9 Aspect Ratio Calculator: The missing dimension for a 16:9 frame. Resolution Scale Calculator: Scaled resolution at a percentage. TV Mounting Height Calculator: Bottom and top edge height to center the screen at eye level.
How to use the Screen Size Calculator
- Enter diagonal (in) (above 0).
- Enter aspect ratio width (above 0).
- Enter aspect ratio height (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Diagonal | A number, in in | > 0 |
| Aspect ratio width | A number | > 0 |
| Aspect ratio height | A number | > 0 |
Formula and method
Formula
width = diagonal × aw ÷ √(aw² + ah²)
IEEE-754 double precision; shown to the decimals indicated.
Physical size of the visible area.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Diagonal = 55; Aspect ratio width = 16; Aspect ratio height = 9.
| Result | Value |
|---|---|
| Screen size | 47.94 × 26.96 in |
| In centimeters | 121.8 × 68.5 cm |
| Area | 1,292.6 in² |
Example 2
Inputs: Diagonal = 27; Aspect ratio width = 16; Aspect ratio height = 10.
| Result | Value |
|---|---|
| Screen size | 22.9 × 14.31 in |
| In centimeters | 58.2 × 36.3 cm |
| Area | 327.6 in² |
Example 3
Inputs: Diagonal = 34; Aspect ratio width = 21; Aspect ratio height = 9.
| Result | Value |
|---|---|
| Screen size | 31.25 × 13.39 in |
| In centimeters | 79.4 × 34 cm |
| Area | 418.6 in² |
The first line is the headline result (screen size). Below it the screen Size Calculator lists in centimeters and area, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Worked example
√(16² + 9²) = 18.358. Width = 55 × 16 ÷ 18.358 = 47.94 in and height = 55 × 9 ÷ 18.358 = 26.96 in.
Bezels
Bezels are not included, so the cabinet is a little larger. Ultrawide 21:9 screens of the same diagonal are narrower in height.
How the result changes with diagonal
Holding every other input at the first worked example, this table changes only diagonal. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Diagonal | Screen size | In centimeters | Area |
|---|---|---|---|
| 27.5 | 23.97 × 13.48 in | 60.9 × 34.2 cm | 323.1 in² |
| 55 | 47.94 × 26.96 in | 121.8 × 68.5 cm | 1,292.6 in² |
| 110 | 95.87 × 53.93 in | 243.5 × 137 cm | 5,170.3 in² |
| 220 | 191.75 × 107.86 in | 487 × 274 cm | 20,681.3 in² |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Diagonal: entering "0" shows "Diagonal must be greater than 0." beside that field and no result.
- Aspect ratio width: entering "0" shows "Aspect ratio width must be greater than 0." beside that field and no result.
Choosing between the Screen Size Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [16:9 Aspect Ratio Calculator](/technology/16-9-aspect-ratio/) | Matching size | |
| [Resolution Scale Calculator](/technology/resolution-scale/) | width, height and scale | Scaled resolution |
| [TV Mounting Height Calculator](/technology/tv-mounting-height/) | screen diagonal, aspect ratio width and aspect ratio height | Bottom edge height |
| [TV Height Calculator](/technology/tv-height-calculator/) | screen diagonal, aspect ratio width and aspect ratio height | Screen height |
| [Aspect Ratio Calculator](/technology/aspect-ratio-calculator/) | width and height | Aspect ratio |
Background: networking and display
Network speeds are quoted in bits per second and file sizes in bytes, and a byte is 8 bits, so a 100 Mbps link moves at most 12.5 megabytes per second; real throughput is usually below the advertised rate. Pixel density is the diagonal in pixels divided by the diagonal in inches: a 1920×1080 display of 24 inches is about 92 pixels per inch, and a 3840×2160 display of 27 inches about 163.
Assumptions and limitations
- Bezels are not included
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for diagonal and aspect ratio width to confirm this.
Frequently asked questions
How wide is a 65 inch 16:9 TV?
A 65 inch 16:9 TV is 65 × 16 ÷ 18.358 ≈ 56.7 inches wide and 31.9 inches tall.
Is diagonal the screen only?
Yes. The diagonal is the visible screen, measured corner to corner; the bezel and frame are extra.
How does 4:3 differ?
It is taller for the same diagonal.
What does the Screen Size Calculator calculate?
Width, height and area of a screen from its diagonal and aspect ratio. It returns Screen size, In centimeters and Area.
What formula does the Screen Size Calculator use?
width = diagonal × aw ÷ √(aw² + ah²). Physical size of the visible area.
What do I need to enter in the screen Size Calculator?
You enter Diagonal (in), Aspect ratio width and Aspect ratio height.
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Bezels are not included.
What is an example of a screen Size result?
With diagonal 55, aspect ratio width 16 and aspect ratio height 9, the screen size is 47.94 × 26.96 in.
Related calculators
- 16:9 Aspect Ratio Calculator — The missing dimension for a 16:9 frame.
- Resolution Scale Calculator — Scaled resolution at a percentage.
- TV Mounting Height Calculator — Bottom and top edge height to center the screen at eye level.
- TV Height Calculator — Screen height from diagonal and aspect ratio.
- Aspect Ratio Calculator — Simplest aspect ratio of a width and height.
- TV Viewing Distance Calculator — Viewing distance for a chosen horizontal viewing angle.
- Image Resolution Calculator — Megapixels and print size of an image.
Sources
- OpenStax, Prealgebra 2e (Rice University): perimeter, area, volume, circumference and the Pythagorean theorem
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.