Pixel Density Calculator

How pixel density is calculated

Pixel density is the number of pixels along one inch of the screen, measured diagonally. The calculator takes the diagonal resolution in pixels, which is the square root of width² + height², and divides it by the diagonal size in inches. A 27-inch 2560 x 1440 monitor has a diagonal of about 2,937 pixels, so it lands at 2,937 / 27 ≈ 109 PPI.

PPI (pixels per inch) and DPI (dots per inch) are often used as if they mean the same thing. Strictly, DPI belongs to printers and mice, while PPI describes a screen. For monitors the number is identical.

Common sizes and resolutions

Viewing distance matters as much as PPI

Whether you can see individual pixels depends on how far away you sit. With normal (20/20) vision the eye resolves roughly one arcminute, which works out to this rule of thumb: the distance in inches beyond which pixels blend together is about 3,438 divided by the PPI.

• 92 PPI (24" 1080p): pixels blend from about 37 inches / 95 cm. At a typical desk distance of 60 to 70 cm, text looks slightly soft.
• 109 PPI (27" 1440p): about 32 inches / 80 cm. Close to the sweet spot for a desk monitor.
• 163 PPI (27" 4K): about 21 inches / 54 cm. Pixels are invisible at normal distance, which is why text looks print-sharp.
• Phones at 400+ PPI are held at 25 to 30 cm, so they need far more density than a monitor to look equally sharp.

Pixel density and display scaling

Higher density only helps if text stays a comfortable size. Windows and macOS do that with display scaling, and the right scaling level follows almost directly from the PPI:

• Around 90 to 110 PPI: 100% scaling. Everything is drawn at its native size.
• Around 120 to 140 PPI: 125% scaling on Windows. On macOS this range can look small, because macOS is designed around 1x or 2x scaling.
• Around 160 to 185 PPI: 150% to 175% on Windows, or a "looks like 2560 x 1440" setting on macOS. You get the workspace of a 1440p screen with much sharper text.
• Around 220 PPI and up: 200% scaling. This is where Apple's Retina displays sit, and where macOS text looks its best.

Fractional scaling such as 125% or 150% works well in modern apps, but some older Windows programs still look blurry at those levels. If you use a lot of legacy software, a monitor that suits 100% scaling may be the less frustrating choice.

Which density should you pick?

• Gaming: 27" 1440p (109 PPI) is the usual balance. Higher density means more pixels for the graphics card to render every frame, which costs frame rate.
• Text, code and office work: 140 PPI or more makes long reading sessions noticeably easier on the eyes. 27" 4K is a popular choice.
• Photo editing: high density helps you judge sharpness at 100% zoom, but color accuracy matters more than PPI.
• Large or ultrawide screens: a 34" 3440 x 1440 ultrawide sits at about 110 PPI, the same density as a 27" 1440p monitor, just wider.

Pixel density is one of several specs that decide how a monitor looks. The monitor buying guide covers panel types, refresh rate and HDR, and once the new screen arrives, the dead pixel test is the first thing to run.