Aspect Ratio Calculator
Get the ratio from any width and height — or lock a ratio like 16:9 and solve the missing dimension. With a live shape preview.
Aspect ratio –
How aspect ratios are calculated
A ratio is width and height reduced by their greatest common divisor: 1920×1080 shares a factor of 120, leaving 16:9. Solving a missing side is the same relationship run backwards — width × h ÷ w gives the height for any locked ratio.
From dimensions
Type width and height — the simplified ratio, decimal form and orientation appear live.
From a ratio
Lock a preset like 16:9 or type your own, enter one side, and the other is solved.
Sanity-check visually
The preview rectangle shows the actual shape, so a typo is obvious before you export.
The ratios you'll actually meet
16:9 dominates video, monitors and presentations (1920×1080, 1280×720); 9:16 is its portrait twin for stories and reels (1080×1920). Photography leans 3:2 (from 35mm film) and 4:3 (most phone sensors), cinema stretches to 21:9 and wider, and social feeds love 1:1. When a platform demands a different ratio than your source, you have exactly two honest options: crop to the target ratio, or letterbox with bars — stretching is the one choice that always looks wrong.
Frequently asked questions
How do I calculate an aspect ratio from pixel dimensions?
Divide width and height by their greatest common divisor: 1920 and 1080 share 120, giving 16:9. The calculator does this instantly and also shows the decimal form (1.78:1).
How do I find the height for a 16:9 video at a given width?
Multiply the width by 9 and divide by 16: at 1280 wide that's 720. In the ratio mode, lock 16:9, type either dimension, and the other is solved for you.
What are the most common aspect ratios?
16:9 for video, TV and monitors; 4:3 for older screens and many photos; 21:9 for ultrawide and cinema; 1:1 for square social posts; 9:16 for stories and reels; 3:2 for classic photography.
Why does my resized image look stretched?
Because the new dimensions have a different ratio than the original — the image gets squeezed to fit. Keep the ratio locked when resizing, or crop to the target ratio first.