Aspect Ratio Calculator

Calculate and lock aspect ratios — find width or height from any ratio

What is it and how does it work?

An aspect ratio calculator works out a missing dimension when you want to keep an image, video or element in proportion. You lock a ratio — like 16:9 or 4:3 — and enter one side, and it calculates the other so the shape stays the same. Aspect ratio is the relationship between width and height, and keeping it fixed is what stops a picture from looking squashed or stretched when you resize it. It is the quick maths behind "I need this 1920-wide image at 16:9 — how tall is that?"

The everyday reason this matters is that changing width and height independently distorts content, while scaling both by the same ratio preserves it. The calculator removes the proportion arithmetic — find the height from a width at a given ratio, work out the ratio from two dimensions you already have, or scale a known size up or down cleanly. It is handy for video resolutions, responsive image boxes, print sizing and any layout where something must fit a frame without warping. Everything runs in your browser.

Common use cases

• Resizing without distortion: enter a new width and lock the ratio to get the height that keeps an image in proportion.
• Setting a video resolution: find the height for a given width at 16:9, such as 1920×1080 or 1280×720.
• Finding a ratio: enter a known width and height to see the simplified aspect ratio they form.

Frequently asked questions

What does an aspect ratio like 16:9 mean?

It is the proportion of width to height: for every 16 units of width there are 9 of height. 16:9 is the standard widescreen ratio for video and most screens, while 4:3 is the older squarer format and 1:1 is a perfect square. The numbers describe shape, not size.

How do I find the height from a width at a fixed ratio?

Divide the width by the ratio's width part and multiply by its height part. For 16:9 at 1920 wide: 1920 ÷ 16 × 9 = 1080. The calculator does this for you, so you enter one dimension and the ratio and get the other.

Why does my image look stretched after resizing?

Because the new width and height are not in the original ratio, so the content is squashed in one direction. Locking the aspect ratio scales both dimensions together, which keeps the proportions and prevents the stretched or squished look.

How is a ratio simplified from two dimensions?

The width and height are divided by their greatest common divisor to reduce them to the smallest whole-number ratio — so 1920×1080 simplifies to 16:9. This gives a clean, recognisable ratio rather than the raw pixel numbers.

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