Screen Resolution & PPI Calculator
Resolution and diagonal size in — PPI, aspect ratio, diagonal pixels and megapixels out.
Resize keeping this ratio
Type a new width or a new height — the other field is computed to match the ratio above.
About this calculator
PPI measures pixel density: diagonal pixels (Pythagorean theorem) divided by physical diagonal size. Aspect ratio is width:height reduced to smallest whole numbers. Checked against Apple's published specs (iPhone 6/7/8 ≈326 PPI, 13" MacBook Pro ≈227 PPI) — both match.
A note on ultrawide ratios
Some resolutions don't reduce to a clean marketing name — e.g. 3440×1440 is exactly 43:18, close to but not exactly the advertised 21:9. This tool shows the exact reduced ratio.
Uses
Check a display's real sharpness before buying, identify a resolution's aspect ratio, or resize video/image dimensions without distorting them. Runs entirely locally.