PPI Calculator

Quick Answer

Last updated: 3 November 2026 ·How we calculate this: the screen diagonal in pixels divided by its size in inches

How This PPI Calculator Works

Enter the screen’s resolution in pixels and its diagonal size. The calculator uses the Pythagorean theorem to find the diagonal length in pixels, then divides by the diagonal in inches to get pixels per inch. From that it works out the dot pitch, the physical width and height of the screen, its area, its aspect ratio and the total number of pixels.

How to Use the PPI Calculator

1. Enter the horizontal resolution in pixels.
2. Enter the vertical resolution.
3. Enter the diagonal size and choose inches or cm.
4. Press Calculate.
5. Read the PPI, dot pitch and screen size.

Core Formulas

• Diagonal in pixels: √(width² + height²)
• PPI: diagonal in pixels ÷ diagonal in inches
• Dot pitch (mm): 25.4 ÷ PPI
• Screen width (in): horizontal pixels ÷ PPI
• Screen height (in): vertical pixels ÷ PPI

Key Terms

• PPI: pixels per inch, the pixel density of a screen.
• Resolution: the number of pixels across and down.
• Dot pitch: the distance between pixel centers, in millimeters.
• Diagonal: the screen size measured corner to corner.
• Native resolution: the real number of pixels a screen has.

Worked Example

Find the PPI of a 24-inch 1080p monitor.

• Diagonal in pixels = √(1920² + 1080²) = 2,202.9
• PPI = 2,202.9 ÷ 24 = 91.79
• Dot pitch = 25.4 ÷ 91.79 = 0.2767 mm

Real-Life Examples

• Comparing monitors: a 27-inch 1440p has 109 PPI and a 32-inch 4K has 138 PPI.
• TV shopping: a 65-inch 4K TV has 68 PPI.
• Laptops: a 15.6-inch 1080p screen has 141 PPI.
• Desk space: find the screen’s real width and height before you buy.

PPI vs DPI

• PPI (pixels per inch): describes screens and digital images.
• DPI (dots per inch): describes printers, which use many ink dots per pixel.
• In everyday use: people often say DPI for both.

PPI of Common Screens

Choosing a Screen

• Desk monitors: many people find around 90 to 110 PPI comfortable at normal scaling.
• High PPI monitors: 4K at 27 inches often needs display scaling for readable text.
• Phones: are held close, so they use very high PPI.
• TVs: lower PPI is fine because you sit farther away.

Viewing Distance and Sharpness

Whether you can see single pixels depends on both PPI and how far away you sit. A person with 20/20 vision can pick out details about 1 arcminute (1/60 of a degree) across. Pixels smaller than that, as seen from your seat, blend into a smooth image.

• Blend distance (in): about 3,438 ÷ PPI
• 27-inch 1440p: 109 PPI, so pixels blend beyond about 32 inches
• 65-inch 4K TV: 68 PPI, so pixels blend beyond about 4.2 feet

This is only a guide. Eyesight, content and screen quality all change how sharp a picture looks, but it explains why a large TV can look sharp from the sofa while a monitor of the same resolution looks soft up close.

Common Mistakes to Avoid

• Using the case size. Use the visible screen diagonal.
• Swapping width and height. It does not change PPI, but it changes the width and height shown.
• Mixing centimeters and inches. Choose the right unit for the diagonal.
• Judging by PPI alone. Viewing distance and panel quality matter too.
• Using scaled resolution. Enter the native resolution of the panel.

Frequently Asked Questions

References & Sources