e.g. 16.
e.g. 9.
Output
Output will appear here
Click in the output to select all text
Aspect Ratio Calculator
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This Aspect Ratio Calculator solves the missing dimension in a width/height pair given a target ratio like 16:9 or 4:3 — enter a known width to find the matching height, or a known height to find the matching width. It also works in reverse: enter any width and height and it simplifies them into their reduced ratio (e.g. 1920×1080 simplifies to 16:9). It's useful for sizing video, image, or print dimensions to a standard ratio, or figuring out what ratio an arbitrary set of dimensions actually is. This is a general-purpose numeric ratio tool — for cropping an actual image file to a target ratio, see the site's Image Aspect Ratio & Crop Calculator instead. Everything runs locally in your browser. Scroll down to choose a mode and enter your numbers.
Features
- Solves for a missing width or height from a target ratio
- Simplifies any width×height pair into its reduced ratio
- Works for common ratios like 16:9, 4:3, 21:9, or any custom ratio
- Instant recalculation as you switch modes
Why use this aspect ratio calculator?
- Faster than manual cross-multiplication
- Useful for video, image, and print sizing
- Fully private — nothing uploaded
- Free with unlimited use
Frequently asked questions
How do I find the height for a 1920px-wide 16:9 video?
Choose "Height from width + ratio", enter 1920 as width and 16:9 as the ratio — the result is 1080, the standard Full HD height.
How is a ratio simplified?
The calculator finds the greatest common divisor (GCD) of the width and height and divides both by it — for example, 1920×1080 divides down to 16:9.
What's the difference between this and the Image Cropper's aspect ratio tool?
This tool works with numbers only (solving ratios and dimensions); the Image Aspect Ratio & Crop Calculator works with an actual image to calculate crop boundaries and offsets.
Can I use decimal ratios like 1.78:1?
Yes, enter the ratio as any two positive numbers — they don't need to be whole numbers, though whole-number ratios like 16:9 are more common for video.
Does this resize an actual file?
No, this only calculates numbers; use an image or video editing tool to actually resize a file to the calculated dimensions.