Aspect Ratio Calculator
Resize without distortion — enter one new dimension and get the other, ratio locked. Presets for 16:9, 4:3, 1:1 and more.
Original size
Aspect ratio: 16:9
New size (locked to the same ratio)
Type either dimension — the other adjusts automatically to keep the ratio.
About this tool
Every stretched thumbnail and squashed logo on the internet is an aspect-ratio mistake: someone resized one dimension without adjusting the other proportionally. The fix is one cross-multiplication — new height = new width × original height ÷ original width — and this calculator does it instantly, in either direction.
Enter the original width and height (or tap a preset: 16:9 for video, 4:3, 1:1 square, 9:16 for stories and reels, 21:9 ultrawide, 3:2 photo). The tool shows the simplified ratio immediately — type 1920 × 1080 and it tells you that's 16:9, which is itself a common question ("what ratio is my image?"). Then enter either the new width or the new height, and the missing dimension appears, ratio locked, accurate to two decimals.
The daily uses span design and development: scaling an image to fit a layout slot, sizing a responsive video embed, figuring out the height of a 1280-wide export of a 1920×1080 original (720), checking whether a client's requested banner size will distort their photo, or working out CSS padding-top percentages for fluid embeds (the ratio as a percentage is height ÷ width — the FAQ covers the trick). Runs live in your browser, no upload, no limits.
How to use the Aspect Ratio Calculator
- 1Enter the original width and height, or tap a preset like 16:9.
- 2Check the simplified ratio the tool reports.
- 3Type either the new width or the new height.
- 4Read the matching dimension — the ratio is preserved exactly.
Frequently asked questions
What aspect ratio should I use for video?
16:9 (1920×1080, 1280×720) is the universal standard for YouTube and landscape video. Vertical platforms — Stories, Reels, Shorts, TikTok — use 9:16 (1080×1920). Square 1:1 still performs well in feeds. The presets cover all of these.
How do I find the ratio of my image?
Enter its width and height as the original size — the tool simplifies it immediately using the greatest common divisor. 1920×1080 shows 16:9; 3000×2000 shows 3:2; an odd size like 1366×768 shows its true (less tidy) ratio of 683:384.
Why do my resized images look stretched?
One dimension was changed without proportionally changing the other — forcing a 4:3 photo into a 16:9 slot distorts everything in it. Compute the correct pair here first, then resize; or crop to the target ratio instead of stretching.
How does this relate to the CSS aspect-ratio property?
Modern CSS accepts the ratio directly: aspect-ratio: 16 / 9 on an element keeps it proportional at any width. For the older padding-top hack, the percentage is height ÷ width × 100 — for 16:9 that's 56.25%.
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