Aspect Ratio Calculator

Calculate and convert aspect ratios for images, videos, and responsive containers.

  • Color & Design
  • Runs in your browser
  • Free, no signup

How to use

How to Use Aspect Ratio Calculator

  1. 1

    Enter dimensions

    Type the width and height of your image or video.

  2. 2

    See the ratio

    View the simplified aspect ratio calculated from your dimensions.

  3. 3

    Resize proportionally

    Enter a new width or height and get the matching dimension.

The guide

Tested tool guide Design and color tools Checked July 30, 2026

What Aspect Ratio Calculator does, with a checked example

Aspect ratio compares width with height independent of physical size. The calculator reduces integer dimensions with their greatest common divisor, displays a decimal ratio, and can calculate a missing dimension while preserving the relationship. Presets provide common screen and social-media sizes as convenient starting points.

Worked example

A concrete input and expected output from the current implementation.

Input

Width 1920, height 1080

Expected output

16:9; decimal 1.7778

The greatest common divisor of 1920 and 1080 is 120. Dividing both dimensions by 120 produces 16 and 9.

How the result is produced

1

Reduction uses the greatest common divisor

Rounded positive dimensions are divided by their greatest shared factor. This gives the smallest equivalent whole-number ratio.

2

Scaling preserves a quotient

For a known ratio, new height equals width divided by width-to-height ratio. New width equals height multiplied by that ratio, with pixel results rounded to whole numbers.

Good uses

  • Resize an image without stretching it.
  • Calculate video dimensions for a known frame ratio.
  • Check whether two resolutions share the same shape.

Limits and checks

  • Cropping and proportional resizing are different operations.
  • Pixel aspect ratio can differ from display aspect ratio in legacy video.
  • Preset requirements can change, so confirm destination specifications.

Common questions

Is 1920 x 1080 the same ratio as 1280 x 720?

Yes. Both reduce to 16:9, although their pixel counts and potential sharpness differ.

Why is the calculated dimension rounded?

Raster dimensions normally require whole pixels. Rounding can introduce a tiny ratio difference at small sizes.

References and verification

The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.