FreeToolStation

PPI Calculator

Pixel density from a resolution and a screen size.

Tech Calculators Free, no sign-up Runs in your browser
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Pixel density
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Dot pitch
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Screen size
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Total pixels
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Retina distance
MeasureValue
Whether a screen looks sharp depends on density and viewing distance together. A 27-inch 1440p monitor at 109 PPI looks sharp at arm's length and coarse from six inches, which is why a phone needs three times the density for the same apparent quality.

About the PPI Calculator

PPI Calculator works out the pixel density of a screen from its resolution and diagonal measurement. The maths is Pythagoras: the diagonal in pixels is the square root of the sum of the squares of the two pixel counts, and dividing that by the diagonal in inches gives pixels per inch. Everything else -- dot pitch, physical width and height, megapixels -- follows.

Density alone does not tell you whether a screen looks sharp, because perceived sharpness depends on how far away your eye is. The human eye resolves about one arcminute of angle, so the retina distance shown here is the distance at which individual pixels stop being distinguishable at this density. A 109 PPI monitor crosses that threshold at roughly 32 inches, which is about where a desk puts it, while a phone held at a foot needs well over 300 PPI.

Dot pitch is the same information expressed as the distance between pixel centres, and it is the figure manufacturers quote for industrial and medical displays. Smaller is denser: 0.233 mm is a typical desktop monitor, while a flagship phone is under 0.06 mm.

The page shows its working, not just its answer. Where there is a formula it is printed with your own numbers substituted in, so you can check the result rather than take it on trust -- which is the difference between a calculator you can use for something that matters and one you cannot.

Everything runs inside your browser. What you type is never uploaded, never logged and never stored, and the calculator keeps working if your connection drops after the page has loaded.

How to use the PPI Calculator

  1. Choose diagonal inThe fields below change to match what you pick, so only the figures that matter to your case are asked for.
  2. Enter horizontal pixels, vertical pixels and screen diagonalDecimals are fine, and thousands separators are accepted and ignored.
  3. Read the pixel density, dot pitch and screen sizeThe figures update as you type. The Calculate button is there if you would rather press something, but nothing waits for it.
  4. Copy or check the resultCopy the summary with the copy button, or open the table to check it row by row.

Features

  • Shows pixel density, dot pitch, screen size, total pixels and retina distance together, so you are not running it twice
  • A results table you can read across
  • Updates as you type, with no button to press and no page reload
  • Copy the result in one click
  • Free, no sign-up, and it runs entirely in your browser

Who uses this tool

The ppi calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:

  • Comparing two monitors of different sizes and resolutions
  • Checking whether a 4K panel is worth it at a given size
  • Finding the dot pitch quoted in a display datasheet
  • Working out the physical size of a screen from its diagonal

Frequently asked questions

What is a good PPI for a monitor?

Around 110 is standard and comfortable at desk distance; 140 to 220 looks noticeably sharper. Phones need 300 or more because they are held closer.

Is PPI the same as DPI?

In practice the terms are used interchangeably for screens, but DPI properly refers to printer dots and PPI to display pixels.

What is the retina distance?

The viewing distance at which pixels subtend about one arcminute and become indistinguishable to a typical eye. Closer than that and you can see them.

How do I measure the diagonal?

Corner to corner across the visible panel, not including the bezel. That is how manufacturers quote screen size.

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Checked and rebuilt on 2026-10-14. The method this calculator uses is described in the section above, and corrections go through the contact page.