PPI and DPI Explained: Pixel Density Made Simple

PPI and DPI sound interchangeable, and people use them as if they are, but they measure different things. This guide explains pixel density, how to calculate it, and where PPI and DPI actually differ.

What is PPI (pixels per inch)?

PPI, or pixels per inch, measures how densely packed the pixels are on a screen. It's the number of pixels in one inch of display, so a higher PPI means a sharper, more detailed image. PPI depends on both the resolution and the physical screen size, because the same pixels spread across a bigger panel sit further apart.

What is DPI (dots per inch)?

DPI, or dots per inch, measures how densely packed the dots are in a printed image. It's the print-world equivalent of PPI, describing how many ink dots a printer places in one inch of paper. A higher DPI means a finer, more detailed print.

The two terms get swapped constantly, but PPI belongs to screens and DPI belongs to print.

DPI vs PPI: what's the difference?

The difference is simple: PPI measures screen pixel density, DPI measures print dot density. They describe the same idea, detail per inch, in two different mediums.

When you're talking about a monitor, phone, or TV, PPI is the correct term. When you're talking about a printer or a printed photo, DPI is correct. Software and spec sheets often use "DPI" loosely for screens, which is where the confusion comes from.

How is PPI calculated?

PPI equals the diagonal pixel count divided by the diagonal screen size in inches. You find the diagonal pixel count with the Pythagorean theorem: the square root of the width squared plus the height squared.

For a 27-inch 1440p monitor, the diagonal pixels are about 2937, divided by 27 inches, which gives roughly 109 PPI. Our PPI calculator runs this for any resolution and size in one step.

What is a good PPI for a screen?

A good PPI depends on viewing distance, because screens held closer need more density. For a desktop monitor at arm's length, 90 to 110 PPI looks sharp, and above 140 PPI is excellent. Phones, held much closer, need 300 PPI or more to look crisp, which is why a phone's PPI dwarfs a monitor's.

What is "retina" or high-DPI?

A "retina" or high-DPI display is one whose pixel density is high enough that, at a normal viewing distance, your eye can't pick out individual pixels. The exact threshold depends on distance, so a phone needs far more PPI than a monitor to qualify, because you hold it closer.

Past that threshold, adding more pixels stops being visible, which is why chasing ever-higher PPI has limits. Beyond about 140 PPI on a desktop monitor, the gains get hard to notice. To see your own screen's density, pair the screen resolution checker with the PPI calculator.

Frequently asked questions

What is the difference between PPI and DPI?

PPI (pixels per inch) measures screen pixel density, while DPI (dots per inch) measures print dot density. They describe detail per inch in two mediums. PPI is the correct term for displays; DPI is for printing.

What is a good PPI for a monitor?

For a desktop monitor at arm's length, 90 to 110 PPI looks sharp and above 140 PPI is excellent. A 27-inch 1440p screen at about 109 PPI is a popular sweet spot. Phones need 300+ PPI because you hold them closer.

How do I calculate PPI?

Divide the diagonal pixel count by the diagonal screen size in inches. The diagonal pixel count is the square root of width squared plus height squared. The PPI calculator does it automatically.

Is higher PPI always better?

Up to a point. Higher PPI looks sharper until it passes what your eye can resolve at your viewing distance, after which the benefit fades. Past about 140 PPI on a desktop monitor, the gains are hard to see.

Does PPI depend on screen size?

Yes. PPI depends on both resolution and screen size. The same resolution on a larger screen has lower PPI because the pixels spread further apart, which is why a 24-inch 1080p screen is sharper than a 32-inch 1080p one.