Aspect ratio calculator
Reduce any width and height into a clean ratio.
Media
Media & display converters
Display and media calculators: viewing distance, aspect ratio, DPI to print size and screen dimensions for TVs, monitors and design work.
Last updated: May 2026
Tools in this section
Viewing distance calculator
Estimate how far away a screen should be viewed.
DPI pixels to cm
Turn pixels and DPI into real printed size.
Inch to cm
Still one of the highest-use display and size pages.
Data & storage hub
Useful crossover section for media file sizes and transfer rates.
Display and media work runs into the same handful of questions: what ratio is this screen, how far should you sit from it, and how big will an image print. These tools answer each one directly from the numbers on the spec sheet or the file, so you can size a TV wall, lay out a design, or check a print before sending it.
Understanding display specifications
Screen size, resolution, and pixel density (PPI) are three separate numbers that are often confused. Screen size is the diagonal in inches. Resolution is the pixel grid, for example 1920 x 1080. Pixel density is how many of those pixels fit into each inch of physical screen, calculated as the square root of (width squared plus height squared) divided by the diagonal in inches.
For televisions, 4K (3840 x 2160) has four times as many pixels as Full HD (1920 x 1080). On a 55-inch screen that puts pixel density at about 80 PPI, which is sharp enough that individual pixels are invisible from a viewing distance of 2 metres or more. On a 27-inch monitor at 4K the density rises to about 163 PPI, where sharpness becomes clearly visible at a desk.
DPI and PPI mean the same thing for screens but differ in print context. For printing, 300 DPI is sharp, 150 DPI is acceptable for large-format posters viewed from a distance, and 72 DPI is screen resolution only. The DPI pixels to cm calculator translates pixel dimensions at a given DPI into the physical print size.
| Resolution | Common name | Typical screen size | Approx PPI |
|---|---|---|---|
| 1920 x 1080 | Full HD (1080p) | 24 to 27 inch monitor | 82 to 92 PPI |
| 2560 x 1440 | QHD / 1440p | 27 inch monitor | 109 PPI |
| 3840 x 2160 | 4K UHD (monitor) | 27 to 32 inch | 138 to 163 PPI |
| 3840 x 2160 | 4K UHD (TV) | 55 to 65 inch | 68 to 80 PPI |
| 7680 x 4320 | 8K | 65 to 85 inch TV | 104 to 135 PPI |
Choosing and placing a screen
The standard viewing distance recommendation for 4K content is 1 to 1.5 times the screen diagonal. For a 65-inch TV (165 cm) that is 1.7 to 2.5 metres. Full HD benefits from sitting further back, about 1.5 to 2.5 times the diagonal, because lower pixel density becomes visible up close.
For monitors the relevant number is pixels per inch. Below 90 PPI individual pixels are visible at normal arm length. Between 90 and 140 PPI is typical for productivity monitors. Above 140 PPI, text and icons appear sharp at normal operating-system scaling. If a 4K monitor runs at 200% scaling, all content is rendered at double resolution and shown at half the logical resolution, giving a sharp 1920 x 1080 workspace on the screen with smooth edges.
Aspect ratio matters when fitting video or images to a different screen. 16:9 is the native ratio for YouTube, streaming and all modern widescreen displays. Older broadcast content uses 4:3. Social media vertical formats use 9:16. The aspect ratio calculator scales any width or height to the correct matching dimension without distortion.
Frequently Asked Questions
What does a 16:9 aspect ratio mean?
For every 16 units of width there are 9 of height. Most TVs, monitors and video use 16:9, while older content uses 4:3 and social formats often use 1:1 or 9:16. The aspect ratio calculator reduces any width and height to its simplest ratio.
How far should I sit from my TV?
A common guideline for 4K is about 1 to 1.5 times the screen's diagonal. For a 55-inch TV (140 cm) that is roughly 1.4 to 2.1 metres. Higher resolution lets you sit closer without seeing pixels.
What DPI do I need for printing?
300 DPI is the standard for sharp photo prints, while 150 DPI can be fine for large posters viewed from a distance. The DPI to print size tool turns pixel dimensions into the real printed size.
Why is screen size given as a diagonal?
The headline inch figure is measured corner to corner, not across the width. A 27-inch 16:9 monitor is about 60 cm wide and 34 cm tall, so always check width and height when fitting a screen into a space.
How do I convert a screen size from inches to centimetres?
Multiply inches by 2.54. A 24-inch screen is about 61 cm on the diagonal and a 65-inch TV is about 165 cm. The inch to cm tool handles any value.
What pixel density (PPI) is considered hi-DPI or Retina?
Apple uses Retina for displays above about 220 PPI on phones and 110 PPI on desktop monitors, where individual pixels are not visible at typical use distance. A 4K 27-inch monitor is about 163 PPI, which qualifies. Windows calls the same threshold hi-DPI and applies scaling at similar densities.
What aspect ratio should I use for YouTube videos?
16:9 is the native ratio for YouTube and all modern widescreen TVs and monitors. Export at 1920 x 1080 (Full HD) or 3840 x 2160 (4K) to fill the player without black bars. Vertical content for Shorts or phone screens uses 9:16 instead.
How do I find the width and height of a TV from its diagonal size?
For a 16:9 screen, multiply the diagonal by 0.872 to get the width and by 0.490 to get the height. A 65-inch TV is about 144 cm wide and 81 cm tall without the stand. The aspect ratio calculator can verify any diagonal-to-dimension calculation.