How to Calculate an Aspect Ratio
By Tools Star Hub Editorial Team · Published
Divide the width and the height by their greatest common divisor. What remains is the simplified ratio. If you already know the ratio and one side, the missing side is the known side times the other ratio term, divided by the matching term.
The page does not open or resize an image. Use the same unit for both sides.
How to calculate a ratio
- Choose simplify, find height, or find width. Simplify starts from both sides. The other two modes start from a ratio and one known side.
- Enter sizes greater than 0. Zero and negative sides are rejected.
- Read the reduced ratio. The page scales the sides to whole numbers and divides by their greatest common divisor. A decimal pair can become an integer ratio.
- Or fill in the missing side. Enter the ratio and the side you know. A ratio term of 0, or a term that is not a number, is rejected. The page does not crop or export a file.
Example
16:9 and a square
1920 by 1080 simplifies to 16:9. 1280 by 720 is also 16:9. 1080 by 1080 is 1:1.
A missing side
A 4:3 ratio with a width of 800 has a height of 600. A 16:9 ratio with a height of 1080 has a width of 1920. 1.5 by 1 simplifies to 3:2.
Things to watch
Area is a different calculation
Square footage multiplies the sides into area. This page keeps the shape and drops the common factor.
FAQ
- How do 1920 and 1080 become 16:9?
- Divide both by their greatest common divisor, which is 120. 1920 divided by 120 is 16, and 1080 divided by 120 is 9.
- How do I get the other side?
- Multiply the known side by the other ratio term and divide by the matching term. 800 times 3 divided by 4 is 600.
- Does a decimal size stay decimal in the ratio?
- The sides are scaled to whole numbers first, then reduced. 1.5 by 1 becomes 3:2.
- Will this resize a photo?
- No. It only calculates the ratio or the missing side.
To simplify a size or fill in the missing side, use the Aspect Ratio Calculator.