Aspect Ratio Calculator
Calculate width and height keeping the ratio. Presets 16:9, 4:3, 21:9 and more. It also gives you the simplified ratio.
Built by
Miguel Ángel Colorado Marin (MACM)
Built by
Miguel Ángel Colorado Marin (MACM)
Full-Stack Developer · Guadalajara, España
I develop web apps, digital tools and full projects — from design to deployment.
The aspect ratio calculator helps you keep the exact proportions of an image, video or design when you resize it. Enter the width or the height and you instantly get the other dimension while preserving the original ratio — be it 16:9, 4:3, 21:9, 1:1 or any custom proportion. It's ideal for resizing images without distorting them, preparing videos for YouTube or Instagram, laying out responsive interfaces or sizing a banner. It also shows the simplified aspect ratio of any pair of dimensions, so you know whether your file is 16:9 or something else. All the calculation runs in your browser, instantly and free, with nothing to install and no sign-up.
Features
- ✓Two-way calculation
- ✓Common presets
- ✓Simplified ratio
- ✓Lock width or height
- ✓100% in browser
How to calculate the aspect ratio?
- 1
Set the ratio
Type the ratio (for example 16:9) or pick a common preset with one click.
- 2
Enter one dimension
Type the width or the height in pixels and the other dimension is calculated automatically.
- 3
Lock what you prefer
Choose to lock the width or the height when changing the ratio, to keep that value fixed.
- 4
Read the simplified ratio
Below you'll see the ratio reduced to its simplest form (for example 1920×1080 → 16:9).
Frequently asked questions
What is the aspect ratio?
It's the proportion between the width and height of an image or screen, like 16:9. Keeping it prevents content from distorting when resizing.
What is it for?
To calculate dimensions of videos, images, banners or screens keeping the correct proportion, with no black bars or stretching.
Does it calculate both ways?
Yes. Change the width and the height updates, or the other way around, always keeping the chosen ratio.
Is anything sent to a server?
No. It's a math calculation that happens in your browser. Nothing is uploaded or stored.
Related tools
Embed Aspect Ratio Calculator on your site
Add Aspect Ratio Calculator to any web page with a simple iframe. Free, with attribution to miguelacm.es.
<iframe
src="https://miguelacm.es/embed/aspect-ratio"
width="100%"
height="700"
frameborder="0"
title="Aspect Ratio Calculator — miguelacm.es"
></iframe>