Scale a resolution without distorting it: enter the original width and height, then fill in either the new width or the new height (leave the other blank), and the missing dimension is solved to preserve the ratio — with the simplified ratio and its common name shown alongside. Live as you type.
How it works
An aspect ratio is just width divided by height, held constant while both scale together. 1920×1080, 1280×720, and 3840×2160 are all the same shape: 16:9. Solve for the missing side with a cross-multiply — if 1080 × (1280 ÷ 1920) gives 720, then any width you pick keeps the proportions intact. The tool also reduces your dimensions to their simplest whole-number ratio, so 3840×2160 tells you it’s 16:9 rather than making you eyeball it.
Everyday examples
YouTube thumbnails: 1280×720 is the recommendation — at any width, height is 56.25% of it. Instagram: feed posts are 4:5 (1080×1350), Stories and Reels are 9:16 (1080×1920) — the calculator tells you exactly what a portrait crop of your 3:2 photo becomes. Ultrawide monitors: 3440×1440 is 21:9(ish — technically 43:18), which is why a 2560-wide capture of one lands at about 1072 pixels tall, not 1440. Printing: 4:3 sensors crop cleanly to 3:2 (4×6) or square 1:1; a 2:3 portrait is 3:2 flipped.
Built in-house in plain JavaScript — no widgets, no tracking, nothing you type leaves your device.