Aspect Ratio Calculator
Simplify any resolution to its ratio.
Enter any width and height in pixels to get the simplified aspect ratio (like 16:9) plus the decimal form designers use. It divides both numbers by their greatest common divisor, the same math behind every '16:9' or '4:3' label you have ever seen. Handy for wallpapers, video exports, and CSS work.
How it's calculated
Both dimensions are divided by their greatest common divisor to get the 'W:H' text, and width ÷ height gives the decimal ratio.
Frequently asked questions
What is the most common aspect ratio?
16:9 is the standard widescreen ratio used by TVs, monitors, and YouTube. Older 4:3 screens and most phone photos in portrait are closer to 3:4 or 9:16.
How do I find the width for a given ratio?
Multiply the decimal ratio by the target height. For 16:9 (1.778) at 720 px tall: 1.778 × 720 = 1,280 px wide — the familiar 1280×720.
Is the decimal ratio exact?
It rounds to three decimals, which is precise enough for layout work. The ratio text itself is always exact because it is simplified from the real pixel counts.