PPI Calculator
Enter a resolution and diagonal screen size to get pixels per inch, physical dimensions and dot pitch — updated as you type.
Resolution + diagonal → pixel density, instantly
Browsers can detect resolution and DPR, but not physical screen size. Enter your display size in inches or calibrate with the ruler.
Why pixel density matters
Two displays with identical resolution can look completely different: 1920 × 1080 is razor-sharp on a 6-inch phone (~367 PPI) but visibly pixelated on a 27-inch monitor (~82 PPI). PPI is the number that captures that difference. Compare real devices in our phone screen size chart, or check what your own display reports with the screen size checker.
Frequently asked questions
› How is PPI calculated?
PPI = diagonal resolution in pixels ÷ diagonal size in inches. The diagonal in pixels is √(width² + height²). The calculator above shows the formula worked through your exact numbers.
› What is a good PPI?
It depends on viewing distance. Desktop monitors look sharp from ~90 PPI; laptops from ~150; phones held close benefit from 300+ — Apple's original 'Retina' threshold was 300 PPI at typical phone distance. Most current flagship phones are 400–500 PPI.
› Is PPI the same as DPI?
They're often used interchangeably, but strictly PPI describes display pixel density while DPI (dots per inch) describes printer dot density. For screens, PPI is the correct term.
› Does a higher PPI make text smaller?
Not on modern systems — the OS scales the interface using the device pixel ratio, so higher PPI means sharper rendering at the same visual size, not smaller text.
Related tools
- Aspect Ratio Calculator Calculate and simplify aspect ratios, find missing dimensions, and match against common display formats like 16:9, 16:10 and 21:9 — with a live preview.
- Screen Size Comparison Compare phone, tablet, laptop and monitor screens as proportional overlays — or against your own screen. True-size mode shows devices at real physical size.
- Phone Screen Sizes Filterable chart of phone screen sizes: display inches, resolution, PPI, aspect ratio and viewport for iPhone, Samsung Galaxy, Pixel and more.
- Device Pixel Ratio Checker Check your device pixel ratio (DPR) instantly and understand the difference between CSS pixels and physical pixels, with visual examples.