Aspect Ratio Calculator

Calculate aspect ratio from width and height, or find a missing dimension — free 16:9 calculator.

Find a missing dimension

About

About the Aspect Ratio Calculator

Simplifies a width and height into its lowest-terms aspect ratio, or finds a missing dimension from a known ratio.

Video editors and photographers use it to check what ratio a resolution reduces to before exporting, while designers use it to work out a missing width or height that keeps a layout at the right proportions. It's one of many free converters on Toolapt, and like every tool here, it's free to use with no sign-up and no limit on how many times you run it.

Choose what to view about this tool

Guide

Using the Aspect Ratio Calculator

  1. 1

    Step 1

    To simplify a ratio: enter a width and height and click "Calculate ratio".

  2. 2

    Step 2

    To find a missing dimension: enter the known ratio's width and height, plus the one dimension you already know.

  3. 3

    Step 3

    Click "Calculate other dimension" to get the matching width or height.

  4. 4

    Step 4

    Click Clear to reset the first section and start over.

  • Simplifies any width and height into its lowest-terms ratio, such as 1920×1080 reducing to 16:9
  • Works backward too — given a ratio and one known dimension, it calculates the matching missing dimension
  • Keeps both calculators on one page, so simplifying and solving for a dimension don't need separate tools
  • Accepts any positive width and height, not just common video or photo resolutions
  • Works entirely in your browser — no installs and no sign-up
  • Free to use, with no limit on how many times you run it
  • Fully responsive, so it works just as well on a phone as on a desktop

Video editors

Video editors use the Aspect Ratio Calculator for checking what ratio a resolution simplifies to before choosing an export preset.

Photographers

Photographers use the Aspect Ratio Calculator for working out a crop or print size that keeps the same proportions as the original image.

Designers

Designers use the Aspect Ratio Calculator for finding a missing width or height that keeps a layout, banner or thumbnail at the correct ratio.

Developers

Developers use the Aspect Ratio Calculator for calculating responsive image or video dimensions that preserve a design's intended proportions.

Examples

Aspect Ratio Calculator examples

3 worked examples

01

Standard HD frame

Entering width 1920 and height 1080 simplifies to 16:9, both divided by their greatest common divisor, 120.

02

Classic photo frame

Entering width 4000 and height 3000 simplifies to 4:3, both divided by their greatest common divisor, 1000.

03

Find the missing height

With ratio 16:9 and a known width of 1280, the calculator solves for a height of 720 (1280 × 9 ÷ 16 = 720).

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FAQ

Frequently asked questions

Quick answers to common questions about the Aspect Ratio Calculator.

What does the Aspect Ratio Calculator do?

It simplifies a width and height into a lowest-terms ratio, and separately calculates a missing width or height from a known ratio and one known dimension.

Is the Aspect Ratio Calculator free to use?

Yes. It's free, with no sign-up, no watermark and no limit on how many times you use it.

Is my input safe when I use this tool?

Yes. The numbers you enter are processed entirely on your own device — nothing is sent to a server.

How is the ratio simplified?

The width and height are divided by their greatest common divisor, the same way a fraction is reduced to lowest terms, giving a ratio like 16:9 instead of the raw pixel dimensions.

How does finding a missing dimension work?

Enter the ratio's width and height, plus the one dimension you already know (either width or height), and the calculator solves for the other one using that same ratio.

Can I use this for anything other than video or photos?

Yes. Any width-and-height pair — a print size, a banner ad, a UI component — can be simplified or solved the same way.

Can I use the Aspect Ratio Calculator on my phone?

Yes. The page is fully responsive and works on mobile, tablet and desktop browsers alike.

Does the Aspect Ratio Calculator have any limitations?

It works with any positive numeric width and height; it doesn't validate that a resolution matches a real device or standard.

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