Every screen – TV, monitor, laptop or phone – has a characteristic shape. Manufacturers quote the diagonal size, but two screens with the same diagonal can look very different: a 27-inch 16:9 monitor is about 59.8 × 33.6 cm, while a 27-inch 4:3 screen would be 54.9 × 41.1 cm. Knowing the ratio helps you choose wallpapers, set up video export and judge whether letterbox bars will appear.
There are two ways to find it. With a tape measure, divide the visible width by the visible height and compare the result with the common formats: 1.78 is 16:9, 1.6 is 16:10, 1.33 is 4:3 and about 2.37 is “21:9”. With the resolution from your display settings, the pixel numbers reduce exactly – 2560 × 1440 is 16:9 and 2340 × 1080 is 13:6, which phone makers call 19.5:9.
Add the diagonal in the resolution mode to get the pixel density in pixels per inch and the physical width and height, handy for comparing sharpness or checking whether a screen fits a space.
How to use the Screen Ratio Calculator
- I know
- Screen width (visible area)
- Screen height (visible area)
- Horizontal resolution (px)
- Vertical resolution (px)
- Diagonal screen size (optional)
Everything is calculated in your browser, so results appear instantly and nothing you type is sent to a server.
How it works
The width is divided by the height. For pixel resolutions the two numbers are reduced by their greatest common divisor; for measurements the decimal ratio is matched to the nearest standard format. PPI divides the diagonal in pixels by the diagonal in inches.
Worked example
A 27-inch monitor runs at 2560 × 1440. gcd(2560, 1440) = 160, so the ratio is 16:9. Its diagonal is √(2560² + 1440²) = 2937 px, giving 2937 ÷ 27 = 108.8 PPI. Physical width = 27 × 1.778 ÷ √(1 + 1.778²) = 23.5 in (59.8 cm) and height 13.2 in (33.6 cm).
Screen ratios in practice
| Ratio | Decimal | Typical devices |
|---|---|---|
| 4:3 | 1.33 | iPad, old monitors |
| 3:2 | 1.50 | Microsoft Surface, some laptops |
| 16:10 | 1.60 | MacBook, office monitors |
| 16:9 | 1.78 | TVs, most monitors |
| 19.5:9 | 2.17 | Phones |
| 21:9 | 2.33–2.39 | Ultrawide monitors |
| 32:9 | 3.56 | Super-ultrawide monitors |
Formula
Screen ratio = width ÷ height (reduced with the GCD for pixel resolutions) · PPI = √(pixels wide² + pixels high²) ÷ diagonal (in) · width = diagonal × r ÷ √(1 + r²), height = diagonal ÷ √(1 + r²)
Worked example
Inputs — I know: The resolution in pixels; Horizontal resolution (px): 2,560; Vertical resolution (px): 1,440; Diagonal screen size (optional): 27 in.
Results — Screen ratio = 16:9; Ratio as a decimal (width ÷ height) = 1.7778; Closest standard format = 16:9 – exact match; Written as x:9 = 16 :9; Written as x:10 = 17.78 :10; Pixel density = 108.8 PPI.
Key terms
- Screen ratio
- Width of the visible screen divided by its height.
- Diagonal size
- Corner-to-corner length of the visible screen, the size in adverts.
- PPI
- Pixels per inch along the diagonal; higher means sharper.
Frequently asked questions
What is the ratio of a 1920 × 1080 screen?
16:9 (1.78:1).
What ratio is an iPhone screen?
2556 × 1179 reduces to 284:131, about 2.17:1 – marketed as 19.5:9.
How do I find my screen's ratio?
Look up the resolution in your display settings and enter it, or measure the visible width and height of the panel.
Why can the screen ratio not be negative?
It is a ratio of two lengths, which are always positive.
What is the ratio of a 3440 × 1440 ultrawide?
43:18 (2.39:1), sold as 21:9.
What is the PPI of a 27-inch 1440p monitor?
About 109 PPI; a 27-inch 4K monitor is about 163 PPI.