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Aspect Ratio Calculator

Enter an original width and height to set the ratio. Change either new dimension and the other updates to match, so you can resize without stretching the picture.

Calculate an aspect ratio online free and resize without stretching. Enter an original width and height to set the ratio, change either new dimension, and the other updates to match. It works as an aspect ratio calculator for 16:9, 4:3, 1:1 and vertical formats, giving you the exact pixel size to use. Nothing to download, it all runs in your browser.

Original size

These two numbers set the ratio.

Ratio presets

Aspect ratio

16:9

New size

Change either new dimension and the other stays locked to the ratio.

1280 × 720 keeps the 16:9 ratio.

How it works

  1. 1

    Set the ratio

    Type an original width and height, or tap a preset like 16:9 or 4:3.

  2. 2

    Enter a new size

    Change the new width or the new height. The other value follows the ratio.

  3. 3

    Read it off

    The simplified ratio and matching size update as you type. There is nothing to download.

Instant & 100% private — nothing is uploaded

Your images are processed instantly on your own device and are never sent to a server — so there are no upload waits, no size limits from us, and no copies kept anywhere.

Frequently asked questions

How do I calculate an aspect ratio?
Divide the width and height by their greatest common divisor. For 1920 by 1080 that is 120, which gives 16:9. The tool does that for you and shows the simplified ratio as you type.
What is a 16:9 aspect ratio in pixels?
It is any size where the width divided by the height equals 16 divided by 9. Common examples are 1920×1080, 1280×720 and 3840×2160. Enter one dimension and the calculator fills in the other.
Will this resize my image?
No. It is a calculator that works out the numbers. Take those into an image resizer to change an actual file.
Which ratio presets are included?
You get 16:9, 4:3, 1:1, 9:16, 21:9, 3:2 and 2:3. That covers video, photos, square posts and vertical formats.

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