Best Free Aspect Ratio Calculator
Find a missing width or height from a ratio, or simplify two dimensions to a ratio — free, no signup.
100% free
No signup
No watermark
Files processed in memory, never stored
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How it works
- Choose a mode. Pick "ratio + one side" to find a missing dimension, or "two sides → ratio" to simplify two dimensions.
- Enter your numbers. Type the ratio (e.g. 16:9) and one side, or enter both the width and height.
- Read the result. The missing dimension — or the simplified ratio — updates instantly as you type.
About this tool
Resize without distortion. Enter an aspect ratio such as 16:9 and one dimension — width or height — and the calculator works out the matching side so your image or video keeps its proportions. Or switch modes and enter two dimensions to see the simplified ratio they reduce to. It accepts ratios written with a colon, a slash or an x, and reduces the result to lowest whole-number terms. Everything is computed live in your browser; nothing is sent anywhere.
What people use it for
- Find the height for a given width at 16:9 (or any ratio)
- Simplify two pixel dimensions to a clean ratio like 4:3
- Resize an image or video without stretching it
- Check the aspect ratio of a screen, photo or print size
Frequently asked questions
Choose "ratio + one side", enter a ratio such as 16:9 and one dimension, and it scales the other side to match.
Switch to "two sides → ratio" and enter the width and height; it divides both by their greatest common divisor to show the simplified ratio.
You can write the ratio with a colon (16:9), a slash (16/9) or an x (16x9). All three are read the same way.
Yes. If the dimensions are not whole numbers it expresses the ratio as a value to one — for example 2.35:1.
Resizing to a width and height that share the original ratio prevents stretching or squashing.
No. All the maths happens in your browser, so the numbers never leave your device.
Yes — Aspect Ratio Calculator is completely free, with no watermark on the output and no credit card required.
Yes. It runs in your browser, so Aspect Ratio Calculator works on phones and tablets as well as desktop — there is no app to install.
No. Aspect Ratio Calculator works with no signup at all; an optional free account only exists to unlock higher usage limits.
Usually just a few seconds for a typical file — Aspect Ratio Calculator starts working the moment you give it your input.