Aspect Ratio Calculator
Enter a width and height to find their simplified ratio, plus a proportional height for any new width.
How aspect ratio simplification works
The simplified ratio is found by dividing both the width and height by their greatest common divisor (GCD) — the largest number that divides both evenly — reducing them to the smallest whole numbers that preserve the same proportion, like 1920×1080 reducing to 16:9.
To find a proportional height for a new width, this calculator multiplies the new width by the original height-to-width ratio. This is exactly what image and video editors do internally when you resize with "lock aspect ratio" enabled, preventing stretching or squashing.
Frequently asked questions
Why does 1920×1080 simplify to 16:9?
1920 and 1080 share a greatest common divisor of 120. Dividing both by 120 gives 16 and 9 — the smallest whole numbers in the same proportion, which is why 16:9 is the standard name for this common widescreen ratio.
Why does resizing without matching the aspect ratio distort an image?
If you change width and height independently without keeping their ratio constant, every pixel gets stretched unevenly in one direction more than the other, making circles look like ovals and square objects look rectangular.
Can I use this for ratios other than screen resolutions?
Yes — this works for any two related dimensions, including print sizes, aspect ratios for cropping photos, or scaling physical objects like a scale model proportionally.