Ratio Calculator
Reduce a ratio to its simplest form.
Simplified ratio
Positive whole numbers only.
Formula checked · NumberSwift · Review process
How this calculator works
Reducing a ratio divides both values by their greatest common divisor. The relationship remains the same while the whole numbers become smaller. This is useful for dimensions, proportions and aspect ratios. A ratio alone gives relative scale rather than an absolute size.
Formula
a:b = (a / gcd):(b / gcd)
Assumptions & limitations
Positive whole numbers only.
Worked example
1920:1080 simplifies to 16:9.
To find an actual missing dimension after simplifying the ratio, use the Proportion Calculator.
Our approach to calculations ↗Common questions
Does simplifying change the proportions?
No. Dividing both whole numbers by their greatest common divisor preserves their relationship.
Can I use this for an aspect ratio?
Yes. Enter the image or display width and height as positive whole numbers; 1920:1080 reduces to 16:9.
Does a ratio specify an absolute size?
No. It expresses relative scale; multiple different dimensions can have the same ratio.