Aspect Ratio Calculator
Find the ratio of any width and height, solve a missing side, and get sizes for Reels, TikTok and Shorts.
- Free
- No sign-up
- No watermark
- Runs in your browser
Loading the tool.
Common video sizes and their aspect ratios
Each row is a shape and a size. The shape is the aspect ratio. The size is that shape at 1080 pixels on its short side, which is full HD. The last column is what each platform's own help page says, read in October 2026. Those pages change from time to time, so read the source before a big upload.
| Where it is used | Aspect ratio | Size to export (pixels) | What the platform's help says (checked October 2026) |
|---|---|---|---|
| TikTok | 9:16 | 1080 × 1920 | TikTok Ads Help lists vertical 9:16 as the recommended shape for video ads, at least 540 × 960 pixels. |
| Instagram Reels | 9:16 | 1080 × 1920 | Instagram Help Center says a Reel can be any shape from 1.91:1 to 9:16, with a minimum resolution of 720 pixels and 30 frames per second. |
| Instagram Stories | 9:16 | 1080 × 1920 | Meta's video ad requirements list Stories shapes from 16:9 to 4:5, and 9:16. |
| YouTube Shorts | 9:16 | 1080 × 1920 | YouTube Help says you can upload vertical videos as Shorts, up to 3 minutes long, with a maximum resolution of 1080p. |
| YouTube | 16:9 | 1920 × 1080 | YouTube Help says 16:9 is the standard shape on a computer, and the player adjusts to other shapes. |
| Instagram feed | 4:5 | 1080 × 1350 | Meta's video ad requirements list Instagram feed shapes from 1.91:1 to 4:5, so 4:5 is the tallest. |
| Square post | 1:1 | 1080 × 1080 | TikTok Ads Help lists square 1:1 video ads, at least 640 × 640 pixels. |
The sizes in the third column are our suggestion: the shape at 1080 pixels on the short side. No platform states them as a rule. To find a missing side, multiply the side you know by the other number of the ratio and divide by the matching one: 1080 × 16 ÷ 9 = 1920. A video needs even numbers, so 1000 wide at 9:16 gives 1777.78 tall, which becomes 1778.
How it works
Type your size. Enter the width and the height of your video or picture. The ratio shows at once, with the decimal and, for an odd size, the common shape it is closest to.
Pick a shape. Choose a platform, or type your own ratio. Then give one side of the new size, the width or the height, and the other side is worked out.
Read the crop and the bars. The page shows how much a crop would cut from your video, and how big the bars would be if you keep the whole picture. To do either on a real file, use the video cropper or the video resizer.
What you get
- Solves for the missing side
- Give the width and the shape, or the height and the shape, and the other side appears. It is shown unrounded, rounded to a whole pixel, and rounded to an even one for video.
- Shows what a crop costs
- Before you change a video's shape, see how much of its width or height a crop cuts away, how far the kept part is enlarged, and how thick the bars are if you keep every pixel.
- Reads odd sizes
- A size like 1366 × 768 does not reduce to a short ratio. The page shows the exact ratio, then the common shape it is closest to and how far off it is.
- Takes any unit
- A ratio does not depend on the unit, so you can type pixels, inches or centimetres, and decimals too. The page reads 4.5 × 8 as 9:16.
Questions people ask
How do I calculate an aspect ratio?
Divide the width and the height by the biggest number that goes into both of them. For 1920 × 1080 that number is 120, which leaves 16 and 9, so the ratio is 16:9. The calculator does this as you type, and it works with decimals as well.
What is the aspect ratio of 1920x1080?
It is 16:9, the shape of a standard YouTube video on a computer. Turned on its side, 1080 × 1920 is 9:16, the upright shape used for TikTok, Reels and Shorts. Both sizes have 1080 pixels on the short side.
What size is an Instagram Reel?
Instagram Help Center says a Reel can be any shape from 1.91:1 to 9:16, with a minimum resolution of 720 pixels and 30 frames per second. 9:16 is the tallest of those, and 1080 × 1920 is the full HD size of that shape.
What size should a TikTok video be?
TikTok Ads Help lists vertical 9:16 as the recommended shape for video ads, at least 540 × 960 pixels. 1080 × 1920 is 9:16 at full HD, above that minimum. Square 1:1 and wide 16:9 are listed as well, with their own minimums.
What size is a YouTube Short?
YouTube Help says you can upload vertical videos as Shorts, up to 3 minutes long, with a maximum resolution of 1080p. A 1080 × 1920 video is 9:16 and has 1080 pixels on its short side, so it fits that limit.
How do I change a video's aspect ratio?
There are two ways. A crop cuts the edges until the picture fills the new shape. A fit keeps every pixel and fills the rest with bars. Taking a 1920 × 1080 video to 9:16 at 1080 × 1920, a crop keeps 608 × 1080 of it and a fit leaves bars of 656 pixels above and below. The video cropper and the video resizer do it on a real file.
How do I find the height when I know the width?
Multiply the width by the second number of the ratio and divide by the first. At 9:16 a width of 1080 gives 1080 × 16 ÷ 9 = 1920. If the answer has decimals, round it to a whole pixel, and to an even number for video: 1000 wide at 9:16 comes to 1777.78, which becomes 1778.
Who places the crop?
This page shows what a crop keeps. It does not choose where the crop goes. GPT-Video's auto reframe follows the speaker's face through the video and moves the vertical crop with it, so a person who walks across the frame stays in the shot.
Related
Your file is processed on your device and never uploaded.