How to use the ppi calculator
- Enter the horizontal and vertical pixel counts of the display.
- Enter the diagonal size in inches (the number manufacturers advertise).
- The ppi calculator instantly shows the PPI, dot pitch and physical width and height.
- Use these values to compare sharpness across devices or to set up CSS media queries.
How the PPI formula works
The ppi pixel calculator uses the Pythagorean theorem to find the diagonal resolution in pixels, then divides by the physical diagonal in inches. The formula is:
PPI = sqrt(width² + height²) / diagonal
For a 24-inch monitor at 1920 x 1080, the diagonal resolution is sqrt(1920² + 1080²) = 2202.9 pixels. Dividing by 24 gives 91.79 PPI. Dot pitch, the physical size of one pixel, is simply 25.4 / PPI millimetres, which equals 0.277 mm here.
Common monitor PPI reference table
Use this table as a quick ppi calculator monitor reference when shopping for displays or setting design breakpoints.
| Resolution | Size | PPI | Dot pitch |
|---|---|---|---|
| 1920 x 1080 | 24" | 91.79 | 0.277 mm |
| 2560 x 1440 | 27" | 108.79 | 0.233 mm |
| 3840 x 2160 | 27" | 163.18 | 0.156 mm |
| 3840 x 2160 | 32" | 137.68 | 0.185 mm |
| 2560 x 1600 | 13.3" | 226.98 | 0.112 mm |
Why PPI matters for developers and designers
A ppi screen calculator helps you understand how sharp text and images will appear on a target device. Higher PPI means smaller individual pixels, which makes edges smoother and fine details readable without zooming.
In web development, browsers use a reference pixel defined as 1/96th of an inch. On high-PPI screens the browser applies a device pixel ratio (DPR) so that CSS pixels stay roughly the same physical size. Knowing the exact PPI lets you predict the DPR and test layouts accurately. If you need to convert between CSS units, the pixel to inch converter or em to px converter can help with related math.
PPI versus DPI: what is the difference
PPI (pixels per inch) describes digital displays, while DPI (dots per inch) describes printers. A monitor has fixed pixels, so its PPI is constant regardless of content. A printer places variable ink dots, so DPI can change with quality settings. People sometimes search for a "DPI calculator" when they mean PPI, but the two measure different things. For print-related calculations, see the dedicated DPI calculator.
Calculating physical width and height
Beyond density, this tool derives the actual physical width and height of the screen. Once PPI is known, divide each resolution axis by the PPI value:
Physical width = horizontal pixels / PPIPhysical height = vertical pixels / PPI
For a 1920 x 1080 display at 91.79 PPI, the physical area is about 20.92 inches wide and 11.77 inches tall. These dimensions are useful when mounting monitors side by side or designing kiosk enclosures.
These sizes assume square pixels and that the diagonal you enter is the visible screen diagonal, the number manufacturers advertise. The bezel is not included.
Worked examples
| Example | Input | Result |
|---|---|---|
| 24-inch 1080p monitor | Horizontal pixels: 1920; Vertical pixels: 1080; Diagonal size (inches): 24 | Pixels per inch (PPI): 91.79; Dot pitch: 0.277 mm; Physical width: 20.92 in (53.13 cm); Physical height: 11.77 in (29.89 cm); Diagonal resolution: 2,202.91 px; Total pixels: 2,073,600 (2.07 MP) |
| 27-inch 4K monitor | Horizontal pixels: 3840; Vertical pixels: 2160; Diagonal size (inches): 27 | Pixels per inch (PPI): 163.18; Dot pitch: 0.156 mm; Physical width: 23.53 in (59.77 cm); Physical height: 13.24 in (33.62 cm); Diagonal resolution: 4,405.81 px; Total pixels: 8,294,400 (8.29 MP) |
| 6.1-inch phone (iPhone 14) | Horizontal pixels: 1170; Vertical pixels: 2532; Diagonal size (inches): 6.1 | Pixels per inch (PPI): 457.25; Dot pitch: 0.056 mm; Physical width: 2.56 in (6.50 cm); Physical height: 5.54 in (14.06 cm); Diagonal resolution: 2,789.25 px; Total pixels: 2,962,440 (2.96 MP) |
| 13.3-inch laptop (MacBook Air) | Horizontal pixels: 2560; Vertical pixels: 1600; Diagonal size (inches): 13.3 | Pixels per inch (PPI): 226.98; Dot pitch: 0.112 mm; Physical width: 11.28 in (28.65 cm); Physical height: 7.05 in (17.90 cm); Diagonal resolution: 3,018.87 px; Total pixels: 4,096,000 (4.10 MP) |
FAQ
What does a ppi calculator do?
It computes the pixel density of a screen in pixels per inch using the resolution and diagonal measurement. It also provides dot pitch and physical dimensions.
How do I calculate PPI manually?
Square the horizontal and vertical pixel counts, add them together, take the square root, and divide by the diagonal size in inches. The formula is PPI = sqrt(w^2 + h^2) / d.
What is a good PPI for a monitor?
Around 90 to 110 PPI is standard for desktop monitors at typical viewing distances. For laptops and phones held closer, 200 to 450 PPI is common.
Is PPI the same as DPI?
No. PPI refers to the pixel density of a screen, while DPI refers to the dot density of a printed image. They are often confused but measure different output types.
Does a higher PPI always look better?
Higher PPI produces sharper images, but beyond a certain point the human eye cannot distinguish individual pixels at normal viewing distance. The benefit depends on how close you sit to the screen.
Can I use this as a ppi screen calculator for phones?
Yes. Enter the phone's native resolution and advertised diagonal size. The tool works for any rectangular display, including phones, tablets, monitors and TVs.