complete.tools

Pixel Density (PPI) Calculator

Work out the pixels per inch (PPI) of a screen from its resolution and diagonal size, with dot pitch, screen width and screen height.

What this tool does

Work out the pixels per inch (PPI) of a screen from its resolution and diagonal size, with dot pitch, screen width and screen height. You fill in these fields: Horizontal pixels, Vertical pixels, and Diagonal size. It shows pixel density, dot pitch, total pixels, screen width, and screen height.

Inputs

  • Horizontal pixels (px): A whole number. Must be greater than 0. Starts at 1,920 px. The number of pixels across the width of the screen, from the display settings or the product sheet.
  • Vertical pixels (px): A whole number. Must be greater than 0. Starts at 1,080 px. The number of pixels from the top to the bottom of the screen.
  • Diagonal size (in): A number. Must be greater than 0. Starts at 24 in. The screen size measured corner to corner, as sold by the manufacturer.

How to use

  1. Enter the horizontal pixels in px.
  2. Enter the vertical pixels in px.
  3. Enter the diagonal size in in.
  4. Read the result: pixel density, dot pitch, total pixels, screen width, and screen height. It appears once every required field has a valid value.

Worked examples

Example 1. Inputs:

  • Horizontal pixels: 1,920 px
  • Vertical pixels: 1,080 px
  • Diagonal size: 24 in

Results:

  • Pixel density: 91.8 pixels per inch
  • Dot pitch: 0.277 mm (Distance from the centre of one pixel to the next)
  • Total pixels: 2.07 megapixels
  • Screen width: 20.92 in
  • Screen height: 11.77 in

How this is worked out: Diagonal pixels = sqrt(1920^2 + 1080^2) = sqrt(3686400 + 1166400) = sqrt(4852800) = 2202.90717. PPI = 2202.90717 / 24 = 91.7878. Dot pitch = 25.4 / 91.7878 = 0.276725. Megapixels = 1920 x 1080 / 1000000 = 2.0736. Width in = 1920 / 91.7878 = 20.91781. Height in = 1080 / 91.7878 = 11.76627.

Example 2. Inputs:

  • Horizontal pixels: 3,840 px
  • Vertical pixels: 2,160 px
  • Diagonal size: 27 in

Results:

  • Pixel density: 163.2 pixels per inch
  • Dot pitch: 0.156 mm (Distance from the centre of one pixel to the next)
  • Total pixels: 8.29 megapixels
  • Screen width: 23.53 in
  • Screen height: 13.24 in

How this is worked out: Diagonal pixels = sqrt(3840^2 + 2160^2) = 240 x sqrt(16^2 + 9^2) = 240 x sqrt(337) = 240 x 18.35756 = 4405.81434. PPI = 4405.81434 / 27 = 163.1783. Megapixels = 3840 x 2160 / 1000000 = 8.2944.

Example 3. Inputs:

  • Horizontal pixels: 1,000 px
  • Vertical pixels: 1,000 px
  • Diagonal size: 10 in

Results:

  • Pixel density: 141.4 pixels per inch
  • Dot pitch: 0.180 mm (Distance from the centre of one pixel to the next)
  • Total pixels: 1.00 megapixels
  • Screen width: 7.07 in
  • Screen height: 7.07 in

How this is worked out: A square of 1000 by 1000 pixels has diagonal 1000 x sqrt(2) = 1000 x 1.41421356 = 1414.21356. PPI = 1414.21356 / 10 = 141.4214. Megapixels = 1000 x 1000 / 1000000 = 1.

Limitations

  • Uses the width and height in pixels and the diagonal size you enter. The result is only as accurate as those numbers.
  • Screen width and height are worked out from the diagonal and the pixel shape. They assume a flat rectangular screen with no curve or bezel.
  • Gives the density number only. It does not rate a screen as high or low density.

FAQs

Q: What does PPI measure?
A: PPI is the number of pixels in one inch of the screen, measured along the diagonal. The tool counts the diagonal pixels, from the width and height you enter, and divides by the diagonal size in inches.
Q: Where do I find the resolution and diagonal size?
A: The resolution is the pixel count across and down the screen, for example 1920 by 1080. The diagonal size is the screen size in inches, usually given on the product sheet or in the display settings.
Q: What is dot pitch?
A: Dot pitch is the distance in millimetres from the centre of one pixel to the centre of the next. It is 25.4 divided by the PPI.
Q: Does a higher PPI always look sharper?
A: PPI is one measure of sharpness. Viewing distance also changes how sharp a screen looks, and this tool does not model it.

Explore Similar Tools

Explore more tools like this one: