How does the lock work?

When locked, the tool preserves the preset ratio: changing width updates height and vice versa. Unlock to type any two values.

What presets are available?

16:9, 16:10, 4:3, 3:2, 1:1, 21:9, 9:16 (vertical) and 2.39:1 (cinema).

How is the simplified ratio computed?

Using the greatest common divisor (GCD). For decimals like 2.39:1, the tool matches against the nearest common ratio when one is close.

Why doesn't my decimal ratio simplify?

If your dimensions produce an unusual fraction (e.g. 1920×800 = 12:5), the tool shows the exact GCD-simplified fraction, with fallback to decimal form.

Does the visual preview reflect actual size?

The preview is scaled to fit a 140-pixel bounding box, preserving the aspect ratio. It's proportional, not pixel-accurate.

Aspect Ratio Calculator

Find the missing dimension for any aspect ratio.

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See how it works

Watch a quick simulation of this tool in action — no file needed.

How to use Aspect Ratio Calculator

Follow these steps — everything happens instantly in your browser.

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Step 1. Choose a preset aspect ratio (or type your own width and height).
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Step 2. Enter either width or height — the other updates to preserve the ratio.
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Step 3. Toggle the link icon to edit dimensions freely without a preset.
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Step 4. See total pixels and a scaled visual preview of the ratio.