Aspect Ratio Calculator
Enter a width and height — in pixels, inches, or any consistent unit — to find the simplified aspect ratio (like 16:9) and the diagonal measurement.
How the Aspect Ratio formula works
Ratio simplification and diagonal via the Pythagorean theorem:
Simplified ratio = (Width / GCD) : (Height / GCD) Diagonal = √(Width² + Height²)
Step-by-step calculation
- Find the greatest common divisor (GCD) of the width and height.
- Divide both by the GCD to get the simplified ratio.
- Square the width and height, add them together, and take the square root to get the diagonal.
Worked example
A 1920 × 1080 screen: GCD(1920, 1080) = 120, so the simplified ratio is 16:9. Diagonal (in the same units) = √(1920² + 1080²) ≈ 2202.9 units.
Frequently asked questions
Why do most TVs and monitors use 16:9?
16:9 became the standard widescreen ratio for HDTV and most modern displays because it closely matches common cinema aspect ratios and fits typical viewing content well, replacing the older, more square 4:3 standard.
How do I use this to find a TV's screen dimensions from its diagonal size?
If you know the diagonal and the aspect ratio, you can work backward: for 16:9, width ≈ diagonal × 0.872 and height ≈ diagonal × 0.490 — this calculator's direct input is width/height to ratio, but the same triangle relationship applies in reverse.