TAHA Engineering Toolsby TAHA Knowledge Lab

Computer & IT

Screen PPI & Pixel Density Calculator

Pixels per inch, dot pitch and physical size of a screen from resolution and diagonal.

Inputs

The visible diagonal, as advertised (usually in inches).

Result

Pixel density
91.788PPI (pixels per inch)
Pixels per centimetre
36.14px/cm
Dot (pixel) pitch
0.2767
Physical width
53.13
Physical height
29.89
Total pixels
2,073,600 (2.074 megapixels)
Aspect ratio
16 : 9 (1.778 : 1)

This screen has about 91.788 PPI (pixels per inch), a dot pitch of 0.2767 mm and a visible area of 53.13 cm × 29.89 cm.

Educational estimate — check the assumptions below.

About this calculator

Pixel density, in pixels per inch (PPI), tells you how sharp a screen looks: the same resolution on a smaller screen gives more pixels per inch. Enter the resolution and the diagonal size to compare monitors, laptops, phones or the HMI panel on a machine.

Formula

Diagonal in pixels = √(W² + H²)

PPI = diagonal in pixels ÷ diagonal in inches    Dot pitch = 25.4 mm ÷ PPI

Width = W ÷ PPI    Height = H ÷ PPI (inches)

Worked example

  • 1920 × 1080 at 24″: √(1920² + 1080²) = 2202.9 px ÷ 24 = 91.79 PPI; dot pitch 0.2767 mm; width 53.1 cm, height 29.9 cm.
  • 3840 × 2160 at 27″: 4405.8 ÷ 27 = 163.2 PPI.
  • 2560 × 1440 at 27″: 108.8 PPI.

Assumptions and limitations

  • Assumes square pixels and that the advertised diagonal is the visible image area. Advertised sizes are often rounded (a “24-inch” screen may be 23.8″), so small differences are normal.
  • PPI describes the screen; how sharp it looks also depends on viewing distance and scaling settings.

References

  • Geometry (Pythagoras) applied to the pixel grid; 1 in = 25.4 mm exactly.