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PPI Calculator

Free PPI calculator — Calculate pixels per inch (PPI), pixels per centimeter (PPcm), dot pitch, diagonal pixels, total megapixels, and aspect ratio from screen resolution and diagonal size. Compare pixel density across popular devices.

Device Presets

Pixels Per Inch

91.79

PPI

Pixels Per Centimeter: 36.14

1920×1080

24.0″

92 PPI

Pixels Per Inch

91.79

PPI

Pixels Per Centimeter

36.14

PPcm

Pixels Per Square Inch

8,425

PPI²

Pixels Per Square cm

1,306

PPcm²

Diagonal Pixels

2,202.91

px

Total Megapixels

2.07

MP

Dot Pitch

0.2767

mm

Aspect Ratio

16:9

1.7778:1

Physical Screen Dimensions

Screen Width

20.92″

53.13 cm

Screen Height

11.77″

29.89 cm

Total Pixels

2,073,600

2.07 MP

PPI Comparison Across Devices

Compare pixel density across popular phones, tablets, laptops, monitors and TVs. Click any row to calculate that device above.

DeviceResolutionDiagonalPPIDot Pitch
iPhone 15 Pro1179×25566.1″461.40.055 mm
iPhone 15 Pro Max1290×27966.7″459.60.055 mm
Samsung Galaxy S241080×23406.2″415.70.061 mm
iPad Pro 11"2388×166811″264.80.096 mm
iPad Pro 13"2752×206412.9″266.70.095 mm
MacBook Air 13"2560×166413.6″224.50.113 mm
MacBook Pro 16"3456×223416.2″254.00.100 mm
FHD Monitor 24"1920×108024″91.80.277 mm
4K Monitor 27"3840×216027″163.20.156 mm
4K TV 55"3840×216055″80.10.317 mm
4K TV 65"3840×216065″67.80.375 mm
1080p TV 32"1920×108032″68.80.369 mm

What Is PPI (Pixels Per Inch)?

PPI is a measure of pixel density or resolution of a computer screen, television screen or other display device. Pixels per inch (PPI) or pixels per centimeter (PPcm) indicates how many pixels are in a 1 inch line or 1 cm line on a display.

The PPI Calculator finds pixels per inch (PPI) and pixels per centimeter (PPcm). It will calculate PPI when inches are entered and calculate both PPI and PPcm when centimeters are entered. Also calculated are dot pitch, diagonal in pixels and total number in megapixels.

How to Calculate PPI

Follow these two steps to calculate PPI:

Step 1: Calculate Diagonal in Pixels

Use the Pythagorean Theorem and the screen width and height in pixels to calculate the diagonal length in pixels.

diagonal = √(width² + height²)

Step 2: Divide by Diagonal in Inches

Use the formula to calculate PPI, dividing the length of the diagonal in pixels by the length of the diagonal in inches. The number of pixels per inch or PPI tells you how many pixels are in a 1 inch line on a display screen. The PPI will be the same whether it's a horizontal or vertical or diagonal inch because pixels are square and therefore symmetric. If a display does not have square pixels then this calculator does not apply.

PPI = diagonal in pixels / diagonal in inches

How to Calculate PPI² or Pixels per Square Inch

Multiply PPI × PPI to get pixels per square inch. The number of pixels in a square inch represents the resolution or pixel density of an area of one square inch. Substitute 1 cm for 1 inch to find pixels per square centimeter or PPcm².

Example: Calculate Pixels per Inch PPI

You have a computer screen that is 1920 pixels wide by 1080 pixels high. The diagonal is 10 inches. You want to find the pixel density in one linear inch of display.

diagonal = √(1920² + 1080²)

diagonal = √(3,686,400 + 1,166,400)

diagonal = √4,852,800

diagonal = 2,202.91 pixels

PPI = 2,202.91 / 10

PPI = 220.29

So there are 220.29 pixels in a 1 inch line on the display.

Example: Calculate Pixels per Square Inch, PPI²

Using this same computer screen, PPI² will be:

220.29² = 48,528 pixels per square inch

So there are 48,528 pixels in an area of the screen that is 1 inch wide by one inch high.

How to Calculate Diagonal Dot Pitch

Diagonal dot pitch is the diagonal distance from the center of one pixel to the center of the next. Dot pitch is calculated from the diagonal length in inches and pixels then converted from inches per pixel to millimeters per pixel but normally only expressed in millimeters (mm).

dot pitch = (diagonal in inches / diagonal in pixels) × 25.4 mm/inch

If a screen diagonal is 15.4 inches and has 3396 pixels, dot pitch = (15.4 / 3396) × 25.4 ≈ 0.1152 mm.

How to Calculate Aspect Ratio

For example, let's say you have a screen width equal to 1920 pixels and height equal to 1080 pixels. The ratio of width to height is 1920:1080. To reduce this to lowest terms we find the greatest common factor of 1920 and 1080 which is GCF(1920,1080) = 120. Reduce the ratio of 1920:1080 by dividing both terms by the GCF of 120. 1920/120 = 16 and 1080/120 = 9 so the reduced ratio is 1920:1080 = 16:9.

In some cases we want to know the aspect ratio in terms of 1 as the second term. In that case, divide both terms by the second term to get 1920/1080 = 1.78 and 1080/1080 = 1. The aspect ratio in terms of 1 is 1.78:1 and we can say 1920:1080 = 16:9 = 1.78:1.

Frequently Asked Questions

What is PPI and why does it matter?+
PPI (Pixels Per Inch) measures the pixel density of a display. Higher PPI means more pixels are packed into each inch, resulting in sharper text and images. At typical viewing distances, 300+ PPI makes individual pixels invisible to the human eye (Retina-class), while most desktop monitors range from 90–160 PPI.
What is the difference between PPI and DPI?+
PPI (Pixels Per Inch) refers to the pixel density of a screen display, while DPI (Dots Per Inch) technically refers to the density of dots a printer can produce. In common usage they are often used interchangeably when discussing screens, but strictly speaking PPI is the correct term for displays.
What PPI do I need for sharp text?+
For most desktop monitors at a typical 24-inch viewing distance, 110+ PPI provides good text clarity. For laptops viewed closer, 150+ PPI is recommended. Apple's Retina displays aim for 218+ PPI on laptops and 264 PPI on tablets, making individual pixels indistinguishable at normal viewing distances.
How do I find the PPI of my monitor?+
Look up your monitor's native resolution (e.g. 1920×1080) and diagonal screen size (e.g. 24 inches). Enter these values into our calculator. Alternatively, check your monitor's specifications sheet or settings menu. The PPI of a 24-inch Full HD monitor is approximately 91.79.
What is dot pitch and how does it relate to PPI?+
Dot pitch is the diagonal distance from the center of one pixel to the center of the next, measured in millimeters. It is inversely related to PPI — higher PPI means smaller dot pitch and sharper images. Dot pitch (mm) = 25.4 / PPI. For example, a 220 PPI display has a dot pitch of about 0.115 mm.
Why does the same resolution look different on different screen sizes?+
Because PPI changes with screen size. A 1920×1080 resolution on a 24-inch monitor gives ~92 PPI, but on a 15.6-inch laptop it gives ~141 PPI. The laptop screen packs the same number of pixels into a smaller area, making everything appear sharper. This is why PPI, not just resolution, determines perceived image quality.
Is higher PPI always better?+
Not necessarily. Past a certain PPI at a given viewing distance, the human eye cannot distinguish individual pixels, so additional pixels provide diminishing returns. For desktop monitors viewed at arm's length, 150–200 PPI is excellent. Higher PPI also demands more GPU power to drive additional pixels, which can impact gaming performance.
What is PPcm and when should I use it?+
PPcm (Pixels Per Centimeter) is simply PPI converted to the metric system: PPcm = PPI / 2.54. Use PPcm when working with metric measurements or specifications. For example, a display with 220 PPI has approximately 86.6 PPcm.

How to use PPI Calculator

Simply enter the values in the input fields provided above. Results will update automatically as you type, allowing for instant calculations and side-by-side comparisons.

Our calculators use high-precision mathematical engines to ensure that even the smallest decimal movements are captured accurately.

If you're using this tool on a mobile device, the layout will automatically adjust for touch-friendly interaction. You can save this page to your home screen for quick access.