PPI Calculator

By Calxy · Calculation methodology

Find the pixel density of a monitor, laptop or phone from its resolution and diagonal size, plus dot pitch, physical width and height, and megapixels.

Printed from Calxy · https://www.calxy.net/tech/ppi-calculator

Pixel density91.79 PPI
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1 – 1000000

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0.001 – 100000

Pixel density

91.79 PPI

  • Pixels per centimeter36.14 px/cm
  • Dot pitch0.2767 mm
  • Screen width20.92 in
  • Screen height11.77 in
  • Screen area246.1 in²
  • Total pixels2.07 megapixels

Assumes square pixels and that the advertised diagonal is the visible area. Rounded-corner phone screens and marketing sizes can shift the result by a few PPI.

How this was calculated

Diagonal in pixels = √(1920² + 1080²) = 2,202.90717 px.

PPI = 2,202.90717 px ÷ 24 in = 91.78779875.

Dot pitch = 25.4 mm ÷ 91.78779875 = 0.276725233 mm.

Width = 1920 ÷ 91.78779875 = 20.91781289 in; height = 1080 ÷ 91.78779875 = 11.76626975 in.

Formula

The diagonal in pixels comes from the Pythagorean theorem: d_px = √(width² + height²). Pixel density is that divided by the diagonal size in inches: PPI = d_px ÷ d_in.

Dot pitch, the distance between pixel centers, is 25.4 mm ÷ PPI. The physical width is the horizontal resolution ÷ PPI and the height is the vertical resolution ÷ PPI.

Worked example

A 24-inch 1920 × 1080 monitor: √(1920² + 1080²) = 2,202.9 pixels. 2,202.9 ÷ 24 = 91.79 PPI. Dot pitch is 25.4 ÷ 91.79 = 0.277 mm, and the screen is 20.92 in wide by 11.77 in high with 2.07 megapixels.

A 27-inch 2560 × 1440 monitor has √(2560² + 1440²) ÷ 27 = 108.79 PPI.

Example densities
ScreenResolutionPPI
24 in1920 × 108091.79
27 in2560 × 1440108.79
27 in3840 × 2160163.18

Assumptions

The formula assumes square pixels and that the advertised diagonal is the visible area. Phone screens with rounded corners and marketed sizes rounded to one decimal can make the true value differ by a few PPI. Screen PPI is not the same as printer DPI, which counts ink dots.

How to use the PPI Calculator

Enter the resolution and diagonal size.

  1. Enter the resolution

    Type the horizontal and vertical pixel counts.

  2. Enter the diagonal

    Type the screen size and choose inches or centimeters.

  3. Read the result

    See PPI, dot pitch, physical size, megapixels and the working.

References

Frequently asked questions

What is a good PPI?

It depends on viewing distance. Desktop monitors at arm's length look sharp from about 100 to 110 PPI up; phones held closer typically exceed 400 PPI.

Is PPI the same as DPI?

For screens the terms are often used interchangeably, but strictly PPI counts pixels and DPI counts printed dots. This calculator measures pixels.

Can I enter the diagonal in centimeters?

Yes. Choose centimeters; the calculator divides by 2.54 to get inches before applying the formula.

Last updated . Results are estimates for informational purposes only.