Aspect Ratio Calculator

An aspect ratio is the proportional relationship between an image or screen's width and height. It's written as two numbers separated by a colon (e.g., 16:9). A 16:9 ratio means for every 16 units of width, there are 9 units of height, regardless of actual pixel dimensions.

Enter your original width and height, then enter just the new width (or height) — the other dimension will be calculated automatically to maintain the exact same aspect ratio. This ensures your image or video won't appear stretched or squished.

YouTube recommends 16:9 for standard videos, with a minimum resolution of 1280×720 (720p). The ideal upload resolution is 1920×1080 (Full HD) or higher. YouTube thumbnails should also be 16:9 at 1280×720 pixels.

1080p (1920×1080 pixels) is a 16:9 aspect ratio. You can verify this: gcd(1920, 1080) = 120. 1920÷120 = 16, 1080÷120 = 9. So 1920×1080 simplifies to 16:9.

If you know the desired width and the original aspect ratio: New Height = New Width ÷ (Original Width ÷ Original Height). If you know the desired height: New Width = New Height × (Original Width ÷ Original Height). This calculator handles both automatically.

16:9 means the width is 16 units for every 9 units of height. This is the modern standard widescreen format used by HDTVs, computer monitors, YouTube, and most video content. Other common ratios: 4:3 (older TV/monitors), 1:1 (square, popular on Instagram), 9:16 (vertical/portrait for mobile).