PPI Calculator

What Is PPI (Pixels Per Inch)?

PPI stands for pixels per inch, and it is the standard way to describe the pixel density of a screen. Two displays can share the same 1920 by 1080 resolution yet look very different: squeeze those pixels into a 6-inch phone and text looks razor sharp, stretch them across a 24-inch monitor and individual pixels become visible. That difference is PPI. It tells you how tightly the pixels are packed, which is what your eyes actually perceive as sharpness.

The number comes from the display hardware itself. An LCD panel has a fixed grid of pixels, and an OLED panel has a fixed arrangement of subpixels, so the PPI is baked in at the factory. Software scaling, the "125%" or "150%" setting in Windows or macOS, changes how big things look but never changes the PPI. Apple popularized the idea of "Retina" displays, which is simply marketing for a PPI high enough that individual pixels disappear at a normal viewing distance.

How to Calculate PPI: The Formula

The math uses the Pythagorean theorem. First you find the diagonal resolution in pixels, then you divide by the physical diagonal size in inches:

PPI = square root of (width pixels squared + height pixels squared) / diagonal inches

Take a 27-inch 4K monitor at 3840 by 2160. The diagonal in pixels is the square root of (3840 squared + 2160 squared), which works out to about 4406 pixels. Divide 4406 by 27 and you get about 163.2 PPI. Our calculator above does this in one step, and it also gives you the pixel pitch (25.4 divided by PPI, in millimeters), the total pixel count, the megapixel count, the physical width and height of the panel, and the aspect ratio in both simplified and decimal form.

Worked Example: 24-Inch 1080p Monitor

At 92 PPI, a 24-inch 1080p monitor is fine for general office work at arm's length, but you will notice soft text if you lean in close. If you need your pixel pitch in a different unit, our unit converter turns millimeters into inches and back in seconds.

What Is a Good PPI? Density Tiers Explained

"Good" depends entirely on viewing distance. Your eyes resolve less detail the farther away the screen sits, which is why a TV can get away with 80 PPI while a phone needs 400. Here is how the tiers break down:

For app developers, Android adds another layer: density buckets. LDPI is around 120, MDPI 160, HDPI 240, XHDPI 320, XXHDPI 480, and XXXHDPI 640. Our calculator labels your screen with its nearest bucket, which is handy when you are exporting image assets at the right scale. Curious how a display's megapixels compare as a percentage of 4K or 8K? Run the numbers through our percentage calculator.

PPI vs DPI: What Is the Difference?

People mix these up constantly. PPI is about digital pixels on a screen or in an image file. DPI is about physical dots of ink a printer lays on paper. An inkjet printer rated at 4800 DPI does not produce 4800 pixels per inch of detail; it sprays many tiny ink dots to reproduce each pixel, often 4 to 8 dots per pixel depending on the dithering pattern.

The practical rule for printing: a 300 PPI image printed at 300 DPI looks tack sharp at reading distance, 150 PPI is acceptable for a poster viewed from a few feet away, and billboards get away with under 50 PPI because nobody stands close. Our calculator includes a print mode so you can check whether your photo has enough pixels for the print size you want before you pay for it.

Common Device PPI Reference

Whether you are comparing monitors before a purchase, checking if a photo is print-worthy, or exporting assets for the right Android density bucket, the PPI calculator above gives you the full picture in seconds. Enter your resolution and diagonal size, and you will see PPI, pixel pitch, megapixels, aspect ratio, and a plain-English verdict on sharpness. For unit conversions on pixel pitch or panel dimensions, our unit converter has you covered.

Frequently Asked Questions

What is PPI on a screen?

PPI stands for pixels per inch. It measures pixel density: how many individual pixels fit into one linear inch of a display. A higher PPI means finer detail and sharper text, because each pixel is physically smaller.

What is a good PPI for a monitor?

For a desktop monitor viewed at arm's length, 100 to 140 PPI looks sharp (a 27-inch 1440p monitor is about 109 PPI, a 27-inch 4K monitor about 163 PPI). Phones aim for 300+ PPI because you hold them much closer to your eyes.

What is the difference between PPI and DPI?

PPI describes digital displays and images: pixels per inch on screen. DPI describes printers: dots of ink per inch on paper. A 300 PPI image printed at 300 DPI produces a sharp photo, but the two numbers measure different physical processes.

How do I find my screen resolution?

On Windows, open Settings, then System, then Display, and look at Display resolution. On a Mac, open System Settings, then Displays. For a phone, search the model name plus "specs" on the manufacturer's site to find the native resolution.

Is higher PPI always better?

Up to a point, yes, but with diminishing returns. Beyond about 300 PPI at phone distance or 150 PPI at desk distance, most eyes cannot resolve individual pixels, so extra density adds cost and GPU load without visible benefit.

Last updated: 2026 | Pixel density figures follow the industry-standard diagonal formula. This calculator is for estimation only.