Free tool
Aspect ratio calculator
Type a width and height to get the ratio. Pick a ratio to find the missing side. Or check how much of a video survives a crop to another shape. Everything runs in your browser.
Find the ratio of a size
- Aspect ratio
- 16:9
- Decimal
- 1.7778:1
- Shape
- Landscape.
Find the missing width or height
Change either side and the other one follows the ratio.
Crop or fit to another ratio
Enter your source size and the shape you need. You get the largest crop that fits and the padding that keeps the whole frame.
- Largest crop
- 608 x 1,080 px
- Crop offset, left / top
- 656 / 0 px
- Crop keeps
- 31.7% of the frame
- Fit canvas, no crop
- 1,920 x 3,414 px
- Padding to add
- 1,166 px top, 1,168 px bottom
The crop is centred. Padding is measured at source resolution, so scale the finished canvas down to your export size afterwards. Exact pixel sizes per platform are in the video size guide.
Crop the video itself on Android
Cropzen snaps a clip to 9:16, 1:1, 4:5 or 16:9 and lets you pinch to reframe it. It also trims and batch resizes. 1080p export is free with no watermark or account, and videos stay on your phone. Pro adds 4K.
How aspect ratio works
An aspect ratio is the width of a picture compared with its height. It says nothing about size. A 1280x720 video and a 3840x2160 video have the same 16:9 shape, one just holds nine times as many pixels.
To get the ratio from pixels, find the largest number that divides both sides evenly, the greatest common divisor, and divide by it:
ratio = (width ÷ GCD) : (height ÷ GCD)
For 1920x1080 the GCD is 120, so the ratio is 16:9. The decimal form is width ÷ height, 1.78 here. To find a missing side, flip it around: height = width × ratio height ÷ ratio width. A 1080 px wide 4:5 post is 1080 × 5 ÷ 4 = 1350 px tall.
Some real screens do not reduce to a tidy pair. 1366x768 laptops come out as 683:384, which is close enough to 16:9 that everyone calls it that. The calculator flags these near matches.
Common aspect ratios
| Ratio | Typical resolutions | Where it is used |
|---|---|---|
| 16:9 | 1280x720, 1920x1080, 3840x2160 | YouTube videos, TVs, laptop screens Size pages: YouTube landscape video, X timeline video |
| 9:16 | 1080x1920, 720x1280 | TikTok, Reels, Shorts, Stories Size pages: Instagram Reels, Instagram Stories, TikTok video, YouTube Shorts, Facebook Reels, Pinterest video Pin |
| 4:5 | 1080x1350 | Instagram feed posts, LinkedIn feed video Size pages: Instagram Feed, LinkedIn feed video |
| 1:1 | 1080x1080 | Square posts, profile images, carousel slides |
| 4:3 | 640x480, 1024x768, 1440x1080 | Older TV footage, tablets, default photo mode on most phones |
| 3:2 | 1080x720, 3000x2000, 6000x4000 | Photos from most DSLR and mirrorless cameras, 6x4 prints |
| 21:9 | 2560x1080, 3440x1440 | Ultrawide monitors, cinema-style video |
"21:9" is a marketing label rather than an exact ratio. 2560x1080 works out to 2.37:1 and 3440x1440 to 2.39:1, which matches the wide format many films are shot in.
Turning a horizontal video vertical without losing the subject
A 9:16 crop from a 1920x1080 clip is 608 pixels wide. That is less than a third of the original width, so anything outside that strip is gone. Before cropping, play the clip through and note where the subject moves. A static centre crop works for one person talking to camera. It fails when two people sit at opposite ends of the frame.
If the subject stays in one area, crop and move the box over it. Our guide on cropping a horizontal video to 9:16 on Android walks through that step by step.
If the whole scene matters, fit it instead. The picture keeps its shape and the empty space above and below gets a colour or a blurred copy of the video. The trade-offs are covered in how to resize a video without cropping. Either way, enlarging a 608 px wide crop to 1080x1920 does not add detail, so start from the highest resolution you have.
Questions people ask
How do I calculate an aspect ratio from pixels?
Divide the width and the height by their greatest common divisor. 1920 and 1080 are both divisible by 120, which gives 16 and 9, so 1920x1080 is 16:9. For the decimal form, divide width by height: 1920 / 1080 = 1.78.
What aspect ratio is 1080x1920?
9:16. It is the same pixel count as 1920x1080 turned on its side. Width always comes first, so 1080x1920 is a tall, vertical frame and 1920x1080 is a wide one.
Is 16:9 the same thing as 1080p?
No. 16:9 describes the shape and 1080p describes one size in that shape. 1280x720, 1920x1080 and 3840x2160 are all 16:9. They differ only in how many pixels they hold.
Why round video dimensions to even numbers?
Most H.264 and H.265 video stores colour at half the resolution of brightness in both directions. That only divides cleanly when the width and height are even, so many encoders refuse odd sizes or quietly pad them. Ticking the even option avoids that.
How do I turn a 16:9 video into 9:16 without losing the subject?
Crop a 9:16 box out of the frame and move it to follow the subject. From 1920x1080 that box is 608x1080, about a third of the width. If the scene is too wide for that, fit the whole frame on a 9:16 canvas and fill the space above and below.