TOOLResize without stretching
An aspect ratio is the fixed relationship between width and height. Keep it constant and images, videos and canvases scale cleanly; break it and everything looks squashed. Pick a ratio (or set a custom one), type a width or a height, and this tool gives you the matching dimension instantly.
How it's calculated
Width = height × ratioW ÷ ratioH
For 16:9, a 1920 px width gives 1920 × 9 ÷ 16 = 1080 px — that's Full HD.
Common ratios
- 16:9 — video, YouTube, most monitors and TVs.
- 4:3 — older screens, some presentations.
- 1:1 — square social posts.
- 9:16 — vertical video, stories and reels.
- 21:9 — cinematic ultrawide.
Working with colours too? Try the color converter, or convert numbers between bases with the number base converter.
Frequently asked questions
How do you calculate an aspect ratio dimension?
Multiply the known dimension by the ratio of the other side. For a 16:9 ratio, height = width × 9 ÷ 16. A 1920 pixel width gives a height of 1080.
What is a 16:9 aspect ratio?
16:9 is the widescreen standard for most video, TVs and monitors. For every 16 units of width there are 9 of height, so common sizes are 1280×720, 1920×1080 and 3840×2160.
How do I keep an image in proportion when resizing?
Keep the same aspect ratio. Set the ratio to your original width and height, then change one dimension and read off the other so the image scales without stretching.