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Pixels to Inches Calculator

Physical size of a pixel measurement at a given resolution, in inches, centimetres and points — and the resolution is the whole question.

With pixels 1200 px, resolution 300 dpi, pixels to inches comes to 4.000 in — inches. It is reached in 5 steps, the last of which is pixels / dpi, and each one is printed on the page with its numbers filled in. The formula is the one published by W3C CSS Values and Units, not an approximation fitted to it.

Formula and sources checked · How we check

Pixels 1200 px, Resolution 300 dpi

4.000 in

Inches for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.

It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.

Inches
4.000 in
Inches
pixels / dpi4 in
Centimetres
inches * 2.5410.16 cm
Millimetres
inches * 25.4101.6 mm
Points, at 72 to the inch
inches * 72288 pt
The same pixels at 72 dpi
pixels / 7216.667 in

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Worked example

1,200 pixels at 300 dpi prints 4 inches wide. The same 1,200 pixels at 72 dpi is 16.667 inches — the pixels did not change, only the density they are laid down at, which is why "how big is this image" has no answer without a resolution.

How to work it out yourself

  1. 1.Find the pixel dimension of the image, from its file properties or the editor.
  2. 2.Decide the resolution: 300 dpi for print, 72 dpi for a screen mock-up.
  3. 3.Divide the pixels by the resolution. That is the size in inches.
  4. 4.Multiply by 2.54 for centimetres, or by 72 for typographic points.

The formula

  1. Inchespixels / dpi
  2. Centimetresinches * 2.54
  3. Millimetresinches * 25.4
  4. Points, at 72 to the inchinches * 72
  5. The same pixels at 72 dpipixels / 72

Source: W3C CSS Values and Units — absolute lengths, NIST — international inch, exactly 25.4 mm

Questions people actually ask

Is dpi the same as ppi?
Close enough here. Strictly, ppi counts pixels in an image and dpi counts ink dots a printer lays down, and a printer may use several dots per pixel. For sizing an image the two are used interchangeably.
Why does my image print smaller than it looks on screen?
Because a screen is showing it at roughly 72 to 110 pixels per inch and the printer is packing 300 into the same inch. Same pixels, a third of the width.

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