PPI Calculator (Pixels Per Inch)
Find the pixel density, pixel pitch and total pixel count of a display from its resolution and size.
How to use the PPI Calculator (Pixels Per Inch)
- Enter the horizontal resolution.
- Enter the vertical resolution.
- Enter the diagonal size and pick its unit.
- Press Calculate. The result updates automatically as you type, and you can switch the result unit at any time.
About the PPI Calculator (Pixels Per Inch)
Pixel density describes how sharp a screen looks. More pixels packed into each inch make text and fine lines smoother. Desktop monitors range from about 90 PPI (a 24 in 1080p panel) to over 200 PPI; phones commonly exceed 400 PPI because they are held close to the face.
What matters is density combined with viewing distance. The "pixels blend" distance assumes 20/20 vision, which resolves roughly one arcminute: beyond it, individual pixels cannot be distinguished. A 4K 27 in monitor reaches that point at about 21 in, a typical desk distance, while a 1080p 27 in monitor needs about 42 in. PPI is a property of the screen; DPI properly refers to printer dots, though the terms are often used interchangeably.
Formula
Diagonal in pixels = √(Width² + Height²)
PPI = Diagonal in pixels ÷ Diagonal in inches
Pixel pitch (mm) = 25.4 ÷ PPI
A 27 in 4K monitor has √(3840² + 2160²) = 4,406 pixels along its diagonal, so its density is 4,406 ÷ 27 ≈ 163 PPI and each pixel is about 0.156 mm wide.
Example calculation
Using the default values:
- Horizontal resolution = 3840 px
- Vertical resolution = 2160 px
- Diagonal size = 27 in
the calculator returns:
- Pixel density: 163.2 PPI
- Pixels per centimeter: 64.2 px/cm
- Pixel pitch: 0.1557 mm
- Total pixels: 8.29 megapixels
- Distance where pixels blend (20/20 vision): 21.0674 in
- Screen dimensions: 23.5 × 13.2 in (59.8 × 33.6 cm)
Frequently asked questions
What is a good PPI for a monitor?
Around 100–110 PPI looks fine at normal scaling; 140 PPI and above looks crisp and usually benefits from 125–150% scaling.
What is the PPI of a 27 inch 1440p monitor?
About 109 PPI, since √(2560² + 1440²) ÷ 27 ≈ 108.8.
Is PPI the same as DPI?
Not exactly. PPI counts screen pixels; DPI counts printer ink dots. Many people use DPI loosely for both.
Last updated: · Category: TV & Video calculators