Aspect Ratio Calculator
Calculate the missing width or height to match a target aspect ratio.
What is the Aspect Ratio Calculator?
This tool finds the simplified aspect ratio between a width and height (like 1920×1080 simplifying to 16:9), and calculates the matching height for any new width (or vice versa) while keeping that same ratio.
The math
The ratio simplifies using the greatest common divisor of the width and height. To scale: New Height = New Width × (Original Height ÷ Original Width), which keeps the proportions identical.
How to use it
- Enter a known width and height to see the simplified ratio.
- Enter a new target width (or height) to calculate the matching dimension that keeps the same proportions.
This is useful for resizing images or video without distortion, cropping to a standard ratio, or figuring out what resolution options are available for a given aspect ratio.
Want the "why" behind this tool? Read Why 16:9 and 4:3 Are Both 'Correct' — Just for Different Eras.