DPI to PPI Converter
DPI (dots per inch) and PPI (pixels per inch) both measure resolution, the density of pixels or dots in a printed or displayed image. DPI is typically associated with printers and printing, while PPI is associated with digital displays. Technically, they are equivalent units, and the terms are often used interchangeably. For a digital screen, the PPI depends on the pixel dimensions (width and height) and the physical size of the screen diagonal. A sharper, higher PPI display makes images and text look crisper and clearer. This calculator determines the PPI of a display given its pixel dimensions and diagonal size in inches. Enter the width and height in pixels, the diagonal size in inches, and the calculator shows the PPI. Common screen resolutions are included: a 24-inch 1920x1080 monitor has about 92 PPI, a 27-inch 2560x1440 monitor has about 109 PPI, a 27-inch 4K (3840x2160) monitor has about 163 PPI, and modern smartphones have 326-460 PPI depending on the model and screen size. Understanding PPI helps you choose the right display for your work and understand the sharpness of images on different devices.
Calculation formula
Step 1: Calculate diagonal pixels using Pythagorean theorem:
diagonal_pixels = sqrt(width^2 + height^2)
Step 2: Calculate PPI:
PPI = diagonal_pixels / diagonal_inches
Common screen resolutions and PPI
| Screen size | Resolution | Approximate PPI | Use case |
|---|---|---|---|
| 24" | 1920 x 1080 | 92 | Desktop monitor |
| 27" | 2560 x 1440 | 109 | High-resolution desktop |
| 27" | 3840 x 2160 (4K) | 163 | Professional 4K monitor |
| 32" | 3840 x 2160 (4K) | 138 | Large 4K display |
| 6.1" (iPhone 15 Pro) | 2532 x 1170 | 460 | Smartphone |
| 6.7" (iPad Pro 11") | 2388 x 1668 | 264 | Tablet |
DPI to PPI converter: frequently asked questions
What is the difference between DPI and PPI?
DPI (dots per inch) is used for printers and print output, while PPI (pixels per inch) is used for digital screens. Technically, they measure the same thing: resolution. One DPI and one PPI both equal one dot or pixel per inch. The terms are often used interchangeably.
How do I calculate PPI from screen dimensions?
Use the formula: PPI = sqrt(width^2 + height^2) / diagonal_inches. First, calculate the diagonal using the Pythagorean theorem with the width and height in pixels. Then divide by the screen diagonal size in inches. For example, a 1920x1080 display on a 24-inch screen has approximately 92 PPI.
Why does PPI matter?
PPI affects how sharp and clear images appear on screen. Higher PPI means sharper images and text. Smartphone screens typically have 300-460 PPI, which is why text and images look very sharp. Desktop monitors usually have 90-110 PPI. The human eye can typically distinguish individual pixels below about 300 PPI from normal viewing distances.
What is a good PPI for a monitor?
For comfortable viewing at normal distances (about 24-30 inches), a PPI of 90-120 is good. For high-end displays and close-up work like video editing, 150+ PPI is desirable. Smartphone screens range from 300-460 PPI because they are held much closer to the eye than monitors.
How do I calculate screen diagonal in inches?
If you know the screen width and height in pixels, and the physical diagonal size in inches, you can calculate PPI. If you need the diagonal in pixels, use the Pythagorean theorem: diagonal_pixels = sqrt(width^2 + height^2).
Official sources
- W3C: CSS Values and Units Module Level 3.
- Wikipedia: Pixels per inch.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.