Aspect Ratio Calculator
Reduce a width and height to the simplest whole-number ratio and show the width divided by the height as a decimal.
Recent
Formula
How the calculation works
The tool takes the width and height you enter, checks that both are positive numbers, and then finds their greatest common divisor with the Euclidean method.
Dividing each side by that divisor produces the smallest whole numbers that keep the same proportion, which is printed as a colon ratio such as 16:9.
The decimal value divides the width by the height directly, and widthPerHeight repeats that same figure so a single panel or container can be sized from either reading.
Common mistakes
- Entering a height of zero, since division by zero is undefined and the ratio cannot be reduced, so the calculator rejects it with a clear error.
- Mixing up the order and typing height first, because swapping the pair flips the decimal below one and gives a portrait ratio instead of landscape.
- Treating a decimal result as the reduced ratio, when the colon form is the tidy integer pair and the decimal is only its numeric equivalent.
When to use it
- Video editors and photographers crop footage and stills to fit 16:9, 4:3 or 21:9 frames without stretching the subject inside the picture.
- Web and print designers size images, cards and containers so media keeps its shape when the surrounding layout changes width or height.
Worked example
With the default width 1920 and height 1080 you get the ratio 16:9, a decimal of 1.78 and a width per height of 1.78.
Common questions
What does the ratio value show?
It is the width and height divided by their greatest common divisor, so 1920 by 1080 becomes 16:9.
Why are decimal and widthPerHeight the same?
Both equal width divided by height, reported twice so a designer can read the value in either context.
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