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Aspect Ratio Calculator
Source size
×
Resize keeping the ratio
New width → height
New height → width
calculated client-side · nothing uploaded
// about this tool

Aspect Ratio Calculator Online

Updated 2026-07-09

Calculate aspect ratios online for free. Enter a width and height to get the simplified ratio (like 16:9) and its decimal value, then resize either dimension while keeping the proportions intact. Everything runs in your browser, so nothing you enter is uploaded.

Resizing media is where ratios matter most: change width and height independently and the image stretches. This calculator reduces any size to its simplest ratio using the greatest common divisor, and works both ways — give it a new width and it returns the height that keeps the shape, so photos, videos, and embeds scale cleanly.

// how to use

  1. 1 Enter a source width and height, or pick a preset like 16:9.
  2. 2 Read the simplified ratio and decimal value.
  3. 3 Type a new width or height to get the matching dimension that keeps the same ratio.

// examples

Simplify a resolution
Input
1920 × 1080
Output
16:9 (1.7778)
Resize keeping ratio
Input
ratio 16:9, new width 1280
Output
height 720

// common uses

Resizing images and videos without distortion Finding the height for a given width at a fixed ratio Simplifying a resolution to its aspect ratio Planning responsive media and embeds

// faq

No. Every calculation runs in your browser as you type, so nothing you enter leaves your machine.
The width and height are divided by their greatest common divisor, so 1920 by 1080 reduces to 16 by 9. The decimal value (width divided by height) is shown alongside for quick comparison.
Keep the same ratio. Enter your new width and the calculator gives the height that preserves the proportions — or enter a new height to get the width — so nothing is stretched or squashed.
16 by 9 is standard widescreen video, 4 by 3 is older displays and photos, 1 by 1 is square social posts, and 21 by 9 is ultrawide. The preset buttons load each instantly.
Yes. Because pixels are whole numbers, the calculated width or height is rounded to the nearest pixel, which may shift the ratio by a tiny fraction on unusual sizes.

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