How to use
- Enter a width and height on the left to get the simplest ratio, the decimal ratio and the nearest common ratio.
- On the right, pick or enter a ratio, then type a new width or height; the other side is calculated.
- Click Use this ratio below to carry the ratio from the left into the resize section.
Options explained
- Simplest ratio
- Width and height divided by their greatest common divisor — 1920×1080 becomes 16:9, 2560×1080 becomes 64:27.
- Common ratios
- Shown when the size is within 1.5% of a common ratio such as 16:9, 4:3, 21:9 or 9:16; 1366×768 is close to 16:9, for example.
- Resizing
- Height = new width × ratio height ÷ ratio width. Results can have decimals; video and image sizes are usually rounded to whole numbers, and many encoders need even numbers.
Common sizes and their ratios
| Ratio | Typical sizes | Used for |
|---|---|---|
| 16:9 | 1280×720, 1920×1080, 3840×2160 | HD and 4K video, monitors |
| 16:10 | 1920×1200, 2560×1600 | Some laptops and monitors |
| 4:3 | 800×600, 1024×768 | Older screens, slides |
| 3:2 | 3000×2000, 6000×4000 | Many cameras |
| 1:1 | 1080×1080 | Square posts, avatars |
| 4:5 | 1080×1350 | Portrait feed posts |
| 9:16 | 1080×1920 | Vertical video |
To resize while keeping the ratio, multiply by the ratio of the sides. A 16:9 image at 1280 px wide is 1280 × 9 ÷ 16 = 720 px tall. A 4:5 image at 1080 px wide is 1080 × 5 ÷ 4 = 1350 px tall.
Frequently asked questions
What ratio is 1920×1080?
16:9, the standard for HD video, TVs and most monitors. 1280×720, 2560×1440 and 3840×2160 (4K) have the same ratio.
What ratio is vertical video for Reels, TikTok and Shorts?
9:16, usually 1080×1920.
Why doesn't my 21:9 ultrawide come out as 21:9?
2560×1080 is actually 64:27 (about 2.37:1); it is marketed as the nearby 21:9 (about 2.33:1). 3440×1440 is 43:18 (about 2.39:1).
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