How to use the ppi calculator
- Enter the resolution. Type the screen's pixel width and height, for example 1080 and 2400. Use the Use this device's screen button to estimate it.
- Add the diagonal size. Enter the diagonal in inches, measured corner to corner across the visible screen. Spec sheets list it, such as 6.1 or 27.
- Read the PPI. The big number is pixels per inch. Higher means sharper. The classification tells you how it compares.
- Use the extras. Dot pitch, true physical size and the viewing distance help you compare screens or pick a monitor.
What is PPI?
PPI stands for pixels per inch. It counts how many pixels fit along one inch of a display, so a higher number means finer detail and smoother text. It depends on two things: the resolution of the screen and its physical size. Two screens with the same resolution can have very different PPI if one is much larger.
PPI vs. DPI
PPI describes screens. DPI, dots per inch, describes printers. People often use them interchangeably for monitors, but PPI is the correct term for a display.
What is dot pitch?
Dot pitch is the distance between neighboring pixel centers, in millimeters. It is the inverse view of the same idea: lower dot pitch means more densely packed pixels.
How the retina distance works
A person with normal vision can resolve detail down to about one arc-minute. Dividing 3438 by the PPI gives the distance in inches beyond which individual pixels become indistinguishable. A phone at 460 PPI blends together beyond about 7.5 inches, while a 27-inch 1440p monitor at 109 PPI needs roughly 31 inches.
Want to check a real device? The online ruler helps you measure the physical screen size, and the dead pixel test checks the panel itself.
Frequently asked questions
Take the diagonal of the resolution in pixels, the square root of width squared plus height squared, and divide it by the screen's diagonal size in inches.
Most modern phones sit between 400 and 550 PPI, which is sharp enough that pixels are invisible at normal viewing distance. Above about 300 PPI is generally considered crisp for a phone.
A 27-inch 3840×2160 display is about 163 PPI. A 27-inch 1440p display is about 109 PPI.
No. Resolution is the total number of pixels, such as 1080×2400. PPI also takes screen size into account, so it measures how tightly those pixels are packed.
Only up to a point. Once pixels are smaller than your eye can resolve at your viewing distance, extra PPI mostly costs battery and performance.
Android groups screens into buckets such as mdpi (160), hdpi (240), xhdpi (320), xxhdpi (480) and xxxhdpi (640) so apps can scale assets. The calculator shows the nearest bucket to your PPI.