Aspect Ratio Calculator
Enter a width and height to get the simplified aspect ratio, and a new width to get the matching height.
How aspect ratio works
An aspect ratio is width divided by height. The calculator divides both by their greatest common divisor, so 1920 × 1080 becomes 16:9. To resize without stretching, multiply the new width by height ÷ width: 1280 × 1080 ÷ 1920 = 720.
Common aspect ratios
| Ratio | Decimal | Used for |
|---|---|---|
| 16:9 | 1.778 | HD / 4K TV, YouTube |
| 9:16 | 0.563 | Phone video, Shorts, Reels, TikTok |
| 4:3 | 1.333 | Old TV, iPad |
| 3:2 | 1.500 | 35 mm photo, many laptops |
| 1:1 | 1.000 | Square post |
| 4:5 | 0.800 | Portrait post |
| 21:9 | 2.333 | Ultrawide monitor |
| 16:10 | 1.600 | Laptop / monitor (WUXGA) |
| 2.39:1 | 2.390 | Cinemascope film |
Common resolutions
| Name | Pixels | Ratio |
|---|---|---|
| 720p HD | 1280 × 720 | 16:9 |
| 1080p Full HD | 1920 × 1080 | 16:9 |
| 1440p QHD | 2560 × 1440 | 16:9 |
| 2160p 4K UHD | 3840 × 2160 | 16:9 |
| 4320p 8K UHD | 7680 × 4320 | 16:9 |
| WUXGA | 1920 × 1200 | 8:5 |
| UWQHD | 3440 × 1440 | 43:18 |
| Instagram portrait | 1080 × 1350 | 4:5 |
| Phone video | 1080 × 1920 | 9:16 |
Frequently asked questions
What aspect ratio is 1920×1080?
16:9, the standard for HD and 4K TVs and YouTube. 3840×2160 (4K) and 1280×720 are also 16:9.
What is the ratio for TikTok, Reels and Shorts?
9:16 vertical video, usually 1080 × 1920 pixels.
How do I keep the ratio when resizing?
New height = new width × original height ÷ original width. Resizing 1920×1080 to 1280 wide gives 720 high.