How to use
- Enter the current width and height in the same unit.
- Leave the targets blank if you only want the reduced ratio.
- To resize, enter a target width, a target height, or both.
- Press Calculate. The hero is the reduced ratio.
How it's calculated
The reduced ratio divides the width and height, after scaling to thousandths, by their greatest common divisor. 1920 by 1080 becomes 16:9. A size that does not reduce to small integers still shows a decimal width ÷ height.
Scaled height = target width × original height ÷ original width. Scaled width = target height × original width ÷ original height. Both targets can be filled at once. They are independent questions.
Worked example
1920 by 1080 reduces to 16:9. A target width of 32 in the same proportion has a height of 18, because 32 × 9 ÷ 16 = 18. A square 100 by 100 reduces to 1:1, and a target height of 5 gives a width of 5.
Assumptions
Both sides use the same unit. The reducer looks at thousandths, so a nearly 16:9 photo may reduce to large integers instead of 16:9. The diagonal page handles a screen size in inches along the diagonal.
FAQ
Why didn't 1920×1080 show as 16:9?
It does, when the numbers are exact. A cropped photo such as 1910×1080 will not reduce to 16:9 because it is not that ratio.
Can I enter centimeters?
Yes. The ratio does not care about the unit as long as both sides match.
What is the decimal ratio for?
Width ÷ height. 16:9 is about 1.778. Some specs print that decimal instead of the pair.
Does this crop an image?
No. It only computes sizes. Fitting a photo into a frame that has a different ratio means cropping or leaving a margin, and this page does not choose which.