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Calculate and convert aspect ratios for videos, images, and screens
Quick Presets:
Enter width and height to calculate aspect ratio
| Ratio | Decimal | Common Use | Example Resolution |
|---|---|---|---|
| 16:9 | 1.778 | HD Video, TV, YouTube | 1920×1080 |
| 4:3 | 1.333 | Classic TV, iPad | 1024×768 |
| 21:9 | 2.333 | Ultrawide monitors | 2560×1080 |
| 1:1 | 1.000 | Instagram posts | 1080×1080 |
| 9:16 | 0.563 | Vertical video, Stories | 1080×1920 |
| 16:10 | 1.600 | Computer monitors | 1920×1200 |
| 3:2 | 1.500 | Classic photography | 3000×2000 |
| 2.39:1 | 2.390 | Cinemascope movies | 2048×858 |
Ratio = Width : Height
Decimal = Width ÷ Height
Example: 1920÷1080 = 1.778 (16:9)
Height = Width ÷ Ratio
Example: 1920 ÷ 1.778 = 1080
Width = Height × Ratio
Example: 1080 × 1.778 = 1920
Divide both by GCD
Example: 1920:1080 → 16:9 (GCD=120)
Aspect ratio is the proportional relationship between width and height of an image or screen, expressed as two numbers separated by a colon (e.g., 16:9). It describes the shape of the rectangle. For example, 16:9 means for every 16 units of width, there are 9 units of height. Common aspect ratios include 16:9 (widescreen), 4:3 (standard), and 21:9 (ultrawide).
To calculate aspect ratio: divide both width and height by their greatest common divisor (GCD). For example, 1920×1080: GCD is 120, so 1920÷120 = 16 and 1080÷120 = 9, giving you 16:9. You can also express it as a decimal by dividing width by height: 1920÷1080 = 1.778.
16:9 is a widescreen format (1.778:1 decimal ratio) commonly used for HD TVs, YouTube, and modern displays. It's wider and better for movies. 4:3 is a more square format (1.333:1 decimal ratio) used in older TVs and some tablets. 16:9 provides more horizontal viewing area, while 4:3 is taller and better for portrait content.
To maintain aspect ratio: calculate the ratio (width÷height), then when changing one dimension, calculate the other using the ratio. If new width is 1280 and original ratio is 1.778 (16:9), then new height = 1280÷1.778 = 720. This ensures the image doesn't stretch or distort.
YouTube recommends 16:9 aspect ratio for horizontal videos. The standard resolution is 1920×1080 (Full HD) or 3840×2160 (4K). For vertical videos (YouTube Shorts), use 9:16 aspect ratio with 1080×1920 resolution. YouTube also supports other ratios but may add black bars to fill the 16:9 player.
21:9 (or 2.33:1) is an ultrawide aspect ratio primarily used for ultrawide computer monitors and some movies. Common resolutions include 2560×1080 and 3440×1440. It provides extra horizontal screen space, ideal for productivity (side-by-side windows), gaming (wider field of view), and cinematic movie watching. It's wider than standard 16:9 displays.