PPI/DPI Calculator

Calculate screen PPI from resolution and display size, and check print DPI for optimal quality. Compare pixel density across devices with this free PPI and DPI calculator.

How to Use

  1. Enter resolution

    Input the horizontal and vertical resolution in pixels.

  2. Enter screen size

    Input the diagonal screen size in inches.

  3. View results

    Click Calculate to see PPI, total pixel count, and individual pixel size.

What is PPI (pixel density)?

PPI (Pixels Per Inch) is the number of pixels packed into one inch of a display, and it is the key measure of how detailed a screen looks. The same 4K resolution looks razor-sharp on a 6-inch phone because the PPI is high, but on a 55-inch TV the PPI drops and individual pixels become visible up close. In other words, PPI depends on both resolution and screen size together.

Why it matters

  • Judging sharpness: When comparing devices, resolution numbers alone are not enough; PPI tells you how crisp the image truly is.
  • UI scaling design: On high-PPI screens, drawing in raw pixels would make text far too small, so operating systems apply scaling that matches the PPI.
  • Preparing images: It sets the benchmark for which resolution to export your design assets at.

The formula

PPI is found by dividing the number of pixels along the screen's diagonal by the diagonal length in inches. To get the diagonal pixel count from the width and height in pixels, use the Pythagorean theorem.

PPI = sqrt(width_px^2 + height_px^2) / diagonal_inches

Example: a 24-inch monitor at 1920x1080 resolution:

  • Diagonal pixels = sqrt(1920^2 + 1080^2) = sqrt(4,769,856) ≈ 2202.91
  • PPI = 2202.91 / 24 ≈ 91.8

Width/height in pixels is the screen resolution, and diagonal inches is the physical length measured corner to corner. The total pixel count is shown separately as width x height (about 2.07 million, or 2.07 megapixels).

Frequently Asked Questions

What is the difference between PPI and DPI?
PPI (Pixels Per Inch) describes the pixel density of a screen, while DPI (Dots Per Inch) describes the density of ink dots in print. Screens use PPI and printing uses DPI, although in everyday speech the two terms are often used interchangeably.
How do you calculate PPI?
First find the diagonal pixel count from the width and height (sqrt(width^2 + height^2)), then divide it by the diagonal screen size in inches. For example, a 24-inch monitor at 1920x1080 is about 91.8 PPI.
What are the benefits of a high PPI?
The higher the PPI, the denser the pixels, so the edges of text and images look smoother and sharper. At a normal viewing distance, once you go beyond about 300 PPI it becomes hard to make out individual pixels with the naked eye.
What is a Retina display?
It is an Apple marketing term for a screen whose PPI is high enough that pixels are invisible at a normal viewing distance. Held close, an iPhone qualifies at roughly 326 PPI or more, while a MacBook viewed from farther away qualifies at roughly 220 PPI or more.
What counts as a good PPI?
It depends on the use case. A desktop monitor is fine at 90-110 PPI, a laptop benefits from 150 PPI or more, and a smartphone, held close to the eyes, is best at 300-460 PPI. A TV viewed from a distance is fine at around 80 PPI.
Why does the same 4K have a different PPI on different devices?
Because PPI depends not only on resolution but also on screen size. Packing 3840x2160 (4K) into 6 inches gives about 730 PPI, but spreading it across a 55-inch TV drops it to about 80 PPI. The larger the screen, the more the same pixels are spread out, lowering the density.
What DPI is suitable for printing?
Standard document printing calls for 150-300 DPI, and high-quality photo printing for 300 DPI or more. Large banners and signs viewed from a distance work fine at 72-150 DPI, and the farther the viewing distance, the lower the DPI you can get away with.
What are total pixel count and megapixels?
The total pixel count is width x height, the number of pixels across the whole screen, and dividing that by one million gives the megapixels. For example, 1920x1080 is about 2.07 million pixels, or 2.07 megapixels. Unlike PPI, it depends only on resolution and is independent of screen size.
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