About this PPI Calculator
PPI (Pixels Per Inch) indicates how many pixels are packed into one inch of your screen. A higher PPI means a sharper, clearer image. This metric is crucial for designers, photographers, and gamers choosing monitors or phones.
Who this calculator is for
- Designers, photographers, and developers comparing screen sharpness across devices.
- Shoppers deciding between monitor, tablet, laptop, or phone resolutions.
- Anyone checking whether a target display density is suitable for close-up viewing.
When to use it
- Use it to compare the pixel density of different displays with different sizes and resolutions.
- Use it when deciding if a screen is standard, high-DPI, or phone-grade sharp.
- Use it before designing UI or media for a device with a specific density target.
How to use this calculator
- Enter the Horizontal Pixels (e.g., 1920).
- Enter the Vertical Pixels (e.g., 1080).
- Enter the Diagonal Size in inches (e.g., 24).
- The tool computes the PPI and total Megapixels.
Key assumptions
- Width, height, and diagonal should all be positive values.
- PPI is calculated from the diagonal pixel count divided by the physical screen diagonal in inches.
- The displayed PPI is rounded to the nearest whole number.
Accuracy and testing
Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.
How this calculator works
1. Calculate diagonal resolution using Pythagoras: $d_p = \sqrt{w^2 + h^2}$.
2. Divide by screen size: $PPI = d_p / inches$.
PPI = √(w² + h²) / diagonal
Inputs explained
Resolution
The width and height of the display in pixels. 1920x1080 is Full HD. 3840x2160 is 4K.
Diagonal Size
The advertised screen size, measured from corner to corner.
Understanding your results
Phone: >300 PPI is 'Retina' quality (pixels invisible). Monitor: 90-110 PPI is standard; >140 is high-DPI.
Example scenarios
24-inch 1080p
1920x1080, 24". PPI = 92. Standard desktop sharpness.
iPhone 13
2532x1170, 6.1". PPI = 460. Extremely sharp.
Key Features
- Pythagorean Logic
- Megapixel Count
- Sharpness Estimator
Tips & Best Practices
- If you sit closer to a screen (like a phone), you need a higher PPI for it to look sharp.
- 4K on a 27-inch monitor is 163 PPI, which usually requires UI scaling (150%) to be readable.
Glossary of Terms
- Retina Display
- Marketing term by Apple for a screen with high enough PPI that the human eye cannot distinguish individual pixels at a normal viewing distance.
- DPI
- Dots Per Inch. Often used interchangeably with PPI, though technically refers to printer dots.