Aspect ratio calculator
Work out any image aspect ratio: reduce it to 16:9 style ratios, match common presets, scale to a target width or height, and get the centered crop box or padded canvas size.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Dimensions
Enter the source width and height, then the width or height you want to scale to; crop and padding are centered.
Result
Only integer reduction and rounding are involved; unit conversions follow 1 in = 25.4 mm and 1 in = 96 CSS px.
1280 × 7201080 × 1080 · x=420 y=01920 × 1920Nothing is stretched: the overflow beyond the target ratio is trimmed equally on both sides.
Keeps every pixel and fills the difference with background color.
What this tool does
- A 1920×1080 image has to fit a 4:5 social slot: see exactly how much the crop box trims before deciding between cropping and padding.
- Your design hand-off says "export at 1280 wide": enter the target width and the proportional height comes back, no manual arithmetic.
- Check whether a delivered asset is a standard ratio — 1234×567 is reported as non-standard instead of leaving you with a calculator.
- Cover images, wallpapers and slides: apply a preset size and read off both the source ratio and the target size.
Example
Input
Source 1920 × 1080, target width 1280, crop / pad target ratio 1:1
Output
Simplest ratio 16:9, ratio value 1.7778, common ratio 16:9; scaled to the target width it becomes 1280 × 720; centered crop box 1080 × 1080 (x=420 y=0); padded canvas 1920 × 1920.
Both operations are centered: cropping never stretches the image, padding never drops pixels — pick whichever your layout needs.
Frequently asked questions
Is 16:9 the same as 1.7778?
Yes. 16 ÷ 9 ≈ 1.7778. The simplest ratio is what you get after dividing both sides by their greatest common divisor, while the decimal value makes it easy to compare against other sizes. The tool reports both.
Why is 2048×858 not treated as 21:9?
2048 ÷ 858 ≈ 2.387 against 21 ÷ 9 ≈ 2.333, an error of about 2.3% — well beyond the 0.5% matching tolerance. Marketing calls that size 21:9, but it is really a 2.39:1 cinemascope frame, so the tool reports it as non-standard.
Should I crop or pad?
Crop when the subject sits near the center and the edges are expendable; pad when no pixel may be lost, for example an image with baked-in text. Both results come with exact dimensions you can apply in an image editor.
Why are the scaled numbers not exactly proportional?
The other side is rounded to a whole pixel, so scaling 1920×1080 to 1000 wide gives 1000×563 (the exact value is 562.5). One pixel is invisible on screen and keeps the output on integer dimensions.
Does it read my image?
No. This tool is pure arithmetic: the dimensions you type are processed in the browser, nothing is uploaded and no request is made.
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