Screen Size Checker

What you’re looking at

The big number is your screen’s resolution in CSS pixels — the units websites actually work with. Below it: your current viewport (this browser window, updating live as you resize), your device pixel ratio, the physical pixel count of your display, color depth, orientation, and whether the device reports touch input.

The distinction between those numbers trips up almost everyone. A modern phone might have a gorgeous 1440 × 3200 physical panel but report a 360 × 800 screen, because it renders at a 4× pixel ratio. Both numbers are true; they answer different questions. Our guide on device pixel ratio unpacks it.

The resolution checker

Type any width and height — or click a popular size — and get its aspect ratio, its common name (Full HD, 4K, QHD), and its megapixel count. Useful for checking what a client’s "design for 2560" actually means, or settling which of two monitors has more real estate.

For developers: the live viewport

Because the viewport numbers update as you resize, this page doubles as a quick breakpoint tester. Drag the window edge and watch exactly where your layout should flip. It’s not a replacement for real device testing, but it answers "what width am I actually at?" faster than opening dev tools.

Guides from Screen Size Checker

Longer explainers written for this site. Each one carries a review date.

• The screen sizes that actually matter in 2026 · 5 min read
  Forget the 50-row resolution charts. A handful of sizes cover most of the web’s traffic — here they are, and how to think about the rest.
• Device pixel ratio: why your 4K phone reports 390 pixels · 5 min read
  Physical pixels, CSS pixels, and the 2×/3× multiplier between them — the concept that explains most "why is my image blurry" mysteries.
• Viewport vs screen resolution: the difference that breaks layouts · 4 min read
  Your screen is 1920 wide but your website gets 1050. Where the pixels go, and why designing to "screen sizes" is subtly wrong.
• How to choose responsive breakpoints (without cargo-culting) · 5 min read
  768 and 1024 are fossils of the 2010 iPad. Let content decide where your layout bends, with a sane default set if you must have numbers.
• PPI, retina, and when sharpness stops mattering · 4 min read
  Pixel density decides whether you can see the pixels. The math, the marketing, and the point past which your eyes can’t tell.

See all guides →