PPI Calculator
Pixels per inch of a screen from its resolution and diagonal, with dot pitch and physical size.
Result
Pixels per inch (PPI): 108.79
Assumes square pixels and the picture diagonal as sold.
- Pixels per centimetre
- 42.83
- Dot pitch, centre to centre
- 0.2335 mm
- Diagonal, in pixels
- 2,937.21
- Total pixels, in millions
- 3.6864
- Aspect ratio
- 16:9
- Picture width
- 23.53 in (59.77 cm)
- Picture height
- 13.24 in (33.62 cm)
https://calcgallery.com/everyday-math/ppi-calculator/
Results follow the mathematical operation and values shown. Check that you selected the intended operation, convention and dataset type before relying on the result. Read the full disclaimer
How to use the PPI Calculator
- Enter the screen’s resolution, the pixels across and the pixels down, from its specification.
- Enter the diagonal size in inches or centimetres.
- Read the pixel density in pixels per inch, and the dot pitch, megapixels and physical size that go with it.
The formula
diagonal in pixels = √(W² + H²)PPI = diagonal in pixels ÷ diagonal in inchesdot pitch = diagonal ÷ diagonal in pixelsThe pixel grid has the same shape as the picture when the pixels are square, which almost every modern screen has, so the diagonal in pixels and the diagonal in inches are the same line measured two ways. The same shape gives the physical width and height: the diagonal shared out in the ratio W : H, as the screen size calculator does from an aspect ratio.
Pixels per centimetre
In metric, density is often quoted per centimetre. There are 2.54 centimetres in an inch, so pixels per centimetre is PPI ÷ 2.54; 91.8 PPI is 36.1 pixels per centimetre. The page gives both, whichever unit you enter the diagonal in.
What the numbers do not say
Density is a property of the screen. Whether it looks sharp depends on eyesight and viewing distance, so the page gives no threshold for “sharp enough”. Resolution names such as 4K or QHD are labels for pixel counts; enter the counts themselves.
With your numbers
- Diagonal in pixels = √(2,560² + 1,440²) = 2,937.21
- PPI = 2,937.21 ÷ 27 in = 108.79
Quick reference
Assumes square pixels and the picture diagonal as sold.
| Example | Pixels per inch (PPI) |
|---|---|
| 1920 × 1080 at 24 in | 91.79 |
| 2560 × 1440 at 27 in | 108.79 |
| 3840 × 2160 at 27 in | 163.18 |
| 3840 × 2160 at 65 in | 67.78 |
| 1170 × 2532 at 6.1 in | 457.25 |
| 1920 × 1080 at 60 cm | 93.26 |
Common questions about the PPI Calculator
- How do I calculate PPI?
- Find how many pixels run along the diagonal, then divide by the diagonal’s length in inches. A 1920 × 1080 screen has √(1920² + 1080²) = 2,202.9 pixels corner to corner; at 24 inches that is 2,202.9 ÷ 24 = 91.8 pixels per inch.
- Why does the same resolution look sharper on a smaller screen?
- Because the same number of pixels is packed into less space. A 3840 × 2160 picture is about 163 PPI on a 27-inch monitor and about 68 PPI on a 65-inch TV. How sharp that looks also depends on how far away you sit, which this page does not judge.
- What is dot pitch?
- The distance from the centre of one pixel to the centre of the next, the reciprocal of the density. At 91.8 PPI it is 1 ÷ 91.8 of an inch, about 0.277 mm. A smaller dot pitch means finer pixels.
- Is PPI the same as DPI?
- Not quite. PPI counts the pixels of a screen or a digital image. DPI, dots per inch, counts the ink dots a printer lays down, and a printer may use several dots to make up one pixel’s colour. People often use DPI loosely for both.