DPI Calculator
Calculate screen DPI and PPI from resolution and size
How to Use
- Enter the diagonal screen size in inches
- Input the screen resolution width in pixels
- Input the screen resolution height in pixels
- Click calculate to see DPI, PPI, pixel pitch, and total pixels
What is DPI and PPI?
DPI (Dots Per Inch) and PPI (Pixels Per Inch) are measurements of pixel density that indicate how many pixels or dots are packed into one inch of screen space. For digital screens, DPI and PPI are essentially the same measurement.
Higher DPI/PPI values mean sharper, crisper images and text because more pixels are used to display the same amount of content. Modern high-resolution displays like Retina displays have very high pixel densities, often exceeding 200 PPI.
How DPI is Calculated
DPI is calculated using the Pythagorean theorem to find the diagonal resolution in pixels, then dividing by the diagonal screen size in inches. The formula is: DPI = √(width² + height²) / diagonal size.
For example, a 27-inch monitor with 2560×1440 resolution has: √(2560² + 1440²) / 27 = 2938.55 / 27 ≈ 108.79 DPI.
Why DPI Matters
- Display Quality: Higher DPI results in sharper text and images
- Design Work: Designers need to know DPI for accurate mockups and prototypes
- Gaming: Understanding pixel density helps optimize graphics settings
- Photography: Photographers use DPI to determine optimal viewing distances
- Scaling: Operating systems use DPI to scale UI elements appropriately
- Print vs Screen: Converting between screen and print requires DPI knowledge
Common Screen Resolutions and DPI
| Device | Resolution | Diagonal | Typical DPI |
|---|---|---|---|
| iPhone 15 Pro | 2556×1179 | 6.1" | ~460 PPI |
| MacBook Pro 16" | 3456×2234 | 16" | ~254 PPI |
| 4K Monitor 27" | 3840×2160 | 27" | ~163 PPI |
| Full HD Monitor 24" | 1920×1080 | 24" | ~92 PPI |
| iPad Pro 12.9" | 2732×2048 | 12.9" | ~265 PPI |
Understanding Pixel Pitch
Pixel pitch is the distance between the centers of adjacent pixels, measured in millimeters. It's inversely related to DPI - higher DPI means smaller pixel pitch. The formula is: Pixel Pitch = 25.4mm / DPI.
Smaller pixel pitch results in smoother images and is particularly important for viewing displays at close distances, such as computer monitors or smartphone screens.
Frequently Asked Questions
- What's the difference between DPI and PPI?
- Technically, DPI (Dots Per Inch) refers to printer resolution, while PPI (Pixels Per Inch) refers to screen resolution. However, for digital displays, these terms are often used interchangeably because each pixel on a screen corresponds to a dot. Both measure pixel density.
- What is a good DPI for a monitor?
- For desktop monitors, 90-110 DPI is standard for 1080p displays. High-end displays range from 140-220 DPI (like 4K or 5K monitors). For mobile devices, 300+ DPI is common. The ideal DPI depends on viewing distance - closer viewing requires higher DPI.
- How does DPI affect image quality?
- Higher DPI means more pixels are packed into the same space, resulting in sharper, more detailed images. Text appears crisper, images look smoother, and fine details are more visible. However, higher DPI also requires more graphics processing power and may impact performance.
- Can I change my screen's DPI?
- You cannot change the physical DPI of your screen (it's determined by the panel's resolution and size). However, operating systems allow you to change the scaling/DPI setting, which adjusts how large UI elements appear. This is particularly useful on high-DPI displays to make text and icons readable.
- What is Retina display in terms of DPI?
- Apple's Retina display refers to screens with pixel densities high enough that the human eye cannot distinguish individual pixels at typical viewing distances. This is generally around 220-300+ PPI for laptops and tablets, and 400+ PPI for smartphones held at normal distances.