Aspect ratio calculator
This aspect ratio calculator turns any width and height into an exact ratio and the closest common one, such as 1920 x 1080 = 16:9. It also works out a new width or height at any ratio, so nothing gets stretched.
Find the aspect ratio
Aspect ratio
16:9
- 1.78:1, landscape
- CSS:
aspect-ratio: 16 / 9;
Resize and keep the ratio
Type either side and the other one updates.
What is aspect ratio?
Aspect ratio is the relationship between an image's width and its height, written as width:height. It describes the shape of a video, photo or screen, not its size: 1280 x 720 and 3840 x 2160 have very different pixel counts, but both are 16:9.
How to calculate aspect ratio by hand
- Find the greatest common divisor of the width and height. For 1920 x 1080, that is 120.
- Divide both numbers by it: 1920 / 120 = 16 and 1080 / 120 = 9.
- Write the result as width:height, which gives 16:9.
To resize at the same ratio, use new height = new width x ratio height / ratio width. At 16:9, a width of 1600 gives 1600 x 9 / 16 = 900.
Common aspect ratios and sizes
| Ratio | Decimal | Common sizes (px) | Often used for |
|---|---|---|---|
| 16:9 | 1.78:1 | 1280 x 720, 1920 x 1080, 2560 x 1440, 3840 x 2160 | YouTube videos, TV, most monitors |
| 9:16 | 0.56:1 | 720 x 1280, 1080 x 1920, 2160 x 3840 | Shorts, Reels, TikTok, Stories |
| 4:3 | 1.33:1 | 640 x 480, 1024 x 768, 1440 x 1080 | Older TV and monitors, many tablets |
| 3:2 | 1.50:1 | 1080 x 720, 2160 x 1440, 6000 x 4000 | DSLR and mirrorless photos |
| 16:10 | 1.60:1 | 1280 x 800, 1920 x 1200, 2560 x 1600 | Laptops and desktop monitors |
| 1:1 | 1.00:1 | 720 x 720, 1080 x 1080 | Square social posts and ads |
| 4:5 | 0.80:1 | 720 x 900, 1080 x 1350 | Portrait social feed posts and ads |
| 5:4 | 1.25:1 | 1280 x 1024 | Older desktop monitors |
| 1.85:1 | 1.85:1 | 1998 x 1080 | Widescreen cinema (flat) |
| 2.39:1 | 2.39:1 | 2048 x 858, 4096 x 1716 | Widescreen cinema (scope) |
When the exact ratio looks odd
Many real sizes do not reduce to a tidy ratio. 1366 x 768 is exactly 683:384, and 2560 x 1080 is exactly 64:27, even though they are sold as 16:9 and 21:9. This calculator shows the exact ratio along with how far the size is from the nearest common one.
Changing the aspect ratio of a video
Changing the numbers does not change the footage. To turn a 16:9 video into 9:16, you crop it, add bars or put it over a background, and our free video aspect ratio converter does all three in your browser. For which ratio to use on each platform, see our guide to video aspect ratios for social media. If you would rather have every video reframed by an editor, see our short-form video editing service.
Frequently asked questions
How do you calculate aspect ratio?
Divide the width and the height by their greatest common divisor. For 1920 x 1080 the greatest common divisor is 120, and 1920 / 120 = 16 and 1080 / 120 = 9, so the aspect ratio is 16:9.
What aspect ratio is 1920 x 1080?
1920 x 1080 is exactly 16:9, the standard widescreen shape. So are 1280 x 720, 2560 x 1440 and 3840 x 2160.
What aspect ratio is 1080 x 1920?
1080 x 1920 is exactly 9:16, the same shape as 1920 x 1080 turned on its side. It is the full-screen vertical format used for YouTube Shorts, Instagram Reels and TikTok.
Is 16:9 the same as 1920 x 1080?
No. 16:9 describes a shape, and 1920 x 1080 is one size of that shape. A 1280 x 720 video and a 3840 x 2160 video are also 16:9, with different pixel counts.
How do I find the height from the width and the ratio?
Multiply the width by the ratio's height, then divide by the ratio's width. At 16:9, a width of 1600 gives 1600 x 9 / 16 = 900. To find the width from the height, multiply by the ratio's width and divide by the ratio's height.
Why does 1366 x 768 not come out as 16:9?
Its exact ratio is 683:384, about 0.05% wider than 16:9. Screens at this size are sold as 16:9 because the difference is too small to see, which is why this calculator also shows the closest common ratio.
Is an ultrawide monitor really 21:9?
Not exactly. 21:9 is a marketing label. 2560 x 1080 is exactly 64:27, about 2.37:1, and 3440 x 1440 is exactly 43:18, about 2.39:1. True 21:9 would be about 2.33:1.
Does the calculator work with inches or centimetres?
Yes. An aspect ratio has no units, so any unit gives the right answer as long as width and height use the same one. An A4 page at 29.7 x 21 cm comes out as 99:70, about 1.41:1.