Pixels to PPI Calculator: Pixel Density and Dot Pitch
Calculate PPI from a resolution and screen diagonal in inches or cm. See dot pitch, total pixels and aspect ratio, or work backwards from PPI to find the resolution.
- Pixels per inch (PPI)
- 91.79
- Dot pitch
- 0.2767 mm
- Pixels per cm
- 36.14
- Total pixels
- 2,073,600
- Megapixels
- 2.07 MP
- Aspect ratio
- 16:9
About the Pixels to PPI Calculator
This calculator finds the pixel density (PPI) of a screen from its resolution and its diagonal size. Pixel density tells you how many pixels sit in each inch of the display, so it decides how sharp text looks, how large an interface feels and whether a photo printed or shown on that screen will look crisp. Type the width and height in pixels, choose the diagonal in inches or centimetres, and the result appears at once, together with the dot pitch, the total number of pixels and the reduced aspect ratio.
The maths is the Pythagorean theorem. The diagonal of the pixel grid is the hypotenuse of a right triangle whose sides are the width and the height, and dividing it by the physical diagonal gives pixels per inch:
Here and are the width and height in pixels and is the diagonal in inches. A diagonal given in centimetres is divided by 2.54 first. The dot pitch, the distance between the centres of two neighbouring pixels, follows directly:
How to use it
Calculate PPI
- Pick a preset such as 1080p at 24 in, or type your own Width (px), Height (px) and Screen diagonal.
- Switch Diagonal unit to Centimetres if your spec sheet uses metric sizes.
- Read PPI, dot pitch, pixels per cm, total pixels, megapixels and the aspect ratio in the result grid.
Find the resolution
Choose Find resolution when you know the density and the size but not the pixel grid. Enter the PPI, the diagonal and the aspect ratio, for example 16 and 9, and the calculator returns the width and height rounded to whole pixels.
Worked examples
Example 1: Full HD monitor
A 1920 × 1080 screen with a 24 inch diagonal has a pixel diagonal of 2,202.91 and a density of 2,202.91 / 24 = 91.79 PPI. The dot pitch is 25.4 / 91.79 = 0.2767 mm, the screen holds 2,073,600 pixels and the ratio is 16:9.
Example 2: 4K and 1440p at 27 inches
A 3840 × 2160 panel at 27 inches reaches 163.18 PPI, while a 2560 × 1440 panel of the same size gives 108.79 PPI. The 4K panel packs about 50 percent more pixels into every inch, which is why its text looks noticeably smoother.
Example 3: A phone
A phone with 2556 × 1179 pixels and a 6.1 inch diagonal has 461.44 PPI. At that density the eye can no longer pick out single pixels at a normal reading distance.
Typical pixel densities
Office monitors usually sit between 90 and 110 PPI, high-resolution laptops and 27 inch 4K monitors between 140 and 220 PPI, and recent phones between 400 and 550 PPI. Apple calls a screen "Retina" when the density is high enough that single pixels are hidden at the intended viewing distance, which is why a phone needs far more pixels per inch than a desk monitor.
Why the number matters
A higher PPI makes text and diagonal lines smoother, but it also makes interface elements smaller unless the operating system scales them. Two screens with the same resolution but different sizes have different densities: a 1080p panel is sharp at 14 inches and visibly coarse at 32 inches. Designers also use PPI to choose image sizes, and printers talk about a related figure, dots per inch, when they ask for 300 DPI artwork.
Privacy
Nothing is uploaded; every calculation runs in your browser and never leaves your device. The page keeps no history and needs no account.
Related tools
Use the Length Converter to turn the diagonal into other units, the Area Calculator to work out the screen area, or the Image Resizer to scale pictures to your screen.
Frequently asked questions
How do I calculate PPI from resolution and screen size?
Take the square root of the width squared plus the height squared, both in pixels, and divide it by the screen diagonal in inches. A 1920 × 1080 screen with a 24 inch diagonal gives 2,202.91 / 24 = 91.79 PPI.
What is the PPI of a 27 inch 4K monitor?
A 3840 × 2160 monitor with a 27 inch diagonal has 163.18 PPI. A 27 inch 1440p monitor has 108.79 PPI, so the 4K panel is about 50 percent denser and shows visibly smoother text.
What is dot pitch and how does it relate to PPI?
Dot pitch is the distance between the centres of two neighbouring pixels, measured in millimetres. It equals 25.4 divided by the PPI, so a 91.79 PPI screen has a dot pitch of 0.2767 mm and a denser screen has a smaller pitch.
Can I enter the screen diagonal in centimetres?
Yes. Switch the diagonal unit to centimetres and the calculator divides the value by 2.54 before working out the density. A 60.96 cm diagonal gives exactly the same result as a 24 inch diagonal.
How do I find the resolution from PPI and screen size?
Choose Find resolution, then enter the PPI, the diagonal and the aspect ratio such as 16 by 9. The calculator multiplies PPI by the diagonal to get the pixel diagonal, splits it by the ratio and rounds width and height to whole pixels.
Is a higher PPI always better?
A higher PPI gives smoother text and finer detail, but beyond roughly 300 PPI on a phone or 220 PPI on a monitor most people cannot see the difference at normal distance. Very dense screens also use more power and need operating system scaling.
Does this calculator upload my numbers?
No. Every calculation runs in your browser and nothing is sent to a server, so the values you type never leave your device and the page works without an account.