Free tool · Video
Video Aspect Ratio Calculator
A video's aspect ratio is its width divided by its height, reduced to the smallest whole numbers: 1920 x 1080 is 16:9. Enter a width and height below to get the ratio, scale to a new size with even dimensions, and see exactly how much to crop or pad to reframe 16:9 as 9:16, 1:1 or 4:5. It runs in your browser.
Free, no account required.
Aspect ratio
16:9
Decimal 1.7778, which is 1920 divided by 1080.
Result rounds down to an even number.
Result rounds down to an even number.
Width 1280: 1280 x 720
Height 720: 1280 x 720
Reframe to another ratio
Outer: source frame. Filled: kept window.
Crop window 606 x 1080, starting at x 657, y 0. Output 606 x 1080.
ffmpeg
Filter for your exact numbers (our arithmetic, see the ffmpeg crop filter docs):
-vf "crop=606:1080:657:0"
The Command Generator recipe for this move is fixed to a centred crop or a 1080x1920 canvas:
ffmpeg -i input.mp4 -vf 'crop=ih*9/16:ih' -c:a copy vertical.mp4
Nothing you type leaves your browser.
How the ratio and the scaling are worked out
The ratio is the width and the height divided by their greatest common divisor. For 1920 x 1080 that divisor is 120, which leaves 16 and 9. The decimal, 1.7778, is the width divided by the height and is handy for comparing two shapes: anything above 1 is wider than tall, anything below 1 is taller than wide.
Scaling example. Scale 1920 x 1080 to a width of 1000.
New height = 1000 x 1080 / 1920 = 562.5.
Rounded down to an even number that is 562, so the result is 1000 x 562. A width of 1001 is rounded down to 1000 first, for the same result.
The rule this calculator uses: scale and crop sizes round down to the nearest even integer, padded canvases round up to the nearest even integer, and offsets are the spare space divided by two. The result can differ from the exact ratio by a pixel, which is the price of an even size.
Common video aspect ratios
Six shapes cover almost everything. Where a platform is named, the claim comes from the platform's own help page, checked October 2026: YouTube Help: Recommended upload encoding settings. Where no source is shown, the row is a general description, not a platform requirement. Check the platform you publish on before you rely on a shape.
| Ratio | Decimal | What it is | Source |
|---|---|---|---|
| 16:9 | 1.7778 | Standard widescreen. YouTube Help calls it the standard aspect ratio for YouTube on a computer. | YouTube Help |
| 9:16 | 0.5625 | Full-screen vertical video for phones. YouTube Help says the player adapts to vertical and square uploads. | YouTube Help |
| 1:1 | 1.0000 | Square. YouTube Help says the player adapts to square uploads. | YouTube Help |
| 4:5 | 0.8000 | Portrait, a little taller than wide. Shorter than 9:16, so it fits more of a landscape frame when cropped. | None, general description |
| 4:3 | 1.3333 | The older standard-definition shape, still common in photos and some presentations. | None, general description |
| 21:9 | 2.3333 | Ultrawide, the cinema-style shape sold on wide monitors. The exact ratio of 2560x1080 is 64:27, marketed as 21:9. | None, general description |
Source: https://support.google.com/youtube/answer/1722171. Checked October 2026.
Why encoders need even dimensions
YouTube Help lists chroma subsampling 4:2:0 for H.264 uploads (checked October 2026). In 4:2:0 the brightness channel keeps every pixel while the two colour channels are stored at half the width and half the height. An odd width or height leaves half a colour sample at the edge, and that is why odd sizes are awkward. That explanation is ours; the 4:2:0 setting is YouTube's.
ffmpeg builds the same habit into its scale filter. Its documentation says a negative value such as -2 keeps the aspect ratio while making sure the dimension is divisible by that number (see the scale filter). This calculator does the same job by hand, so the sizes it shows are ones you can type into any editor or encoder without a rounding surprise.
Crop or pad when going vertical
Turning a landscape video into a vertical one means choosing what to lose. A people-in-motion example from the community: a post in r/VideoEditing about converting 16:9 to 9:16 says “A normal crop doesn't work because the subject quickly ends up outside the vertical frame.” That is the limit of a fixed crop, and it is worth knowing before you pick one.
Crop: full screen, sides lost
A 1920 x 1080 source keeps its full 1080 pixel height and gives up width. The 9:16 window is 606 x 1080, starting 657 pixels from the left edge, so it is centred. It fills a vertical screen, but it is only about a third of the original width, so wide scenes and anything near the edges disappear. Scaling 606 x 1080 up to 1080 x 1920 also enlarges the picture, which costs sharpness.
Pad: whole frame, bars added
Keeping all 1920 pixels of width, a 9:16 canvas has to be 1920 x 3414, with the picture placed 1167 pixels down. Nothing is cut, but the picture is a thin strip across the middle of the screen. In practice you scale the whole thing down, which is what a 1080 x 1920 canvas with a 1080 wide picture does. Use it for screen recordings, slides and any frame where the edges carry information.
Our advice, not a rule: crop for a subject in the middle, pad when the whole frame matters, and do not stretch. The ffmpeg crop filter centres the window when you give no x and y, and the pad filter places the picture with x and y. The FFmpeg Command Generator has ready-made 9:16 crop and pad recipes, with every flag explained.
Pixel sizes that match each ratio
A ratio is a shape, and several sizes share one shape. These are the whole-number sizes people reach for, each checked with the formula above. They are arithmetic, not platform requirements.
- 16:9 at 1920 x 1080 and at 3840 x 2160, which is exactly twice as wide and twice as tall.
- 9:16 at 1080 x 1920, the same rectangle turned upright.
- 1:1 at 1080 x 1080, any width equal to its height.
- 4:5 at 1080 x 1350, because 1080 x 5 / 4 is 1350.
- 4:3 at 1440 x 1080, because 1080 x 4 / 3 is 1440.
- 64:27 at 2560 x 1080, the size usually sold as 21:9. A true 21:9 at 1080 pixels high would be 2520 x 1080.
If your size is not in the list, type it into the calculator: it reduces anything to its ratio, so you can see at a glance whether two files share a shape before you decide to crop, pad or scale one of them.
Runs in your browser
This page does arithmetic on numbers you type. It does not ask for a video, it makes no network request when you calculate, and there is no account, watermark or usage cap. If you want to go further, see the other free tools or Linkeddit Studio.
How to calculate a video aspect ratio and reframe it
Step 1
Enter the width and height
Type the pixel dimensions of your video. The simplest ratio and its decimal appear straight away, for example 1920 x 1080 is 16:9.
Step 2
Scale to a new size
Type a target width or a target height. The other side is worked out to keep the ratio, and both numbers round down to even values so encoders accept them.
Step 3
Pick a target ratio and crop or pad
Choose 9:16, 1:1, 4:5 or a custom ratio, then Crop or Pad with bars. The two nested boxes show what is kept, and the ffmpeg filter for your exact numbers is shown below.
When you outgrow this tool
Linkeddit Studio projects come in 1920x1080, 1080x1920, 1080x1080, 3840x2160 or any even custom size.
This calculator is free and complete on its own, with no account. Linkeddit Studio is the desktop editor for the same job on files on your own disk. Studio projects come in 1920x1080, 1080x1920, 1080x1080, 3840x2160 or any even custom size, so you set the shape once when you start the project. Studio is a one-time purchase.
FAQ
Video Aspect Ratio Calculator questions
Direct answers on ratios, scaling, even dimensions and going vertical.
How do I calculate the aspect ratio of a video?
Divide the width by the height to get the decimal, then divide both numbers by their greatest common divisor to get the ratio. 1920 x 1080 has a greatest common divisor of 120, so it reduces to 16:9, a decimal of 1.7778. 2560 x 1080 reduces to 64:27, 2.3704, which is sold as 21:9 but is not exactly 21:9.
How do I resize a video and keep the aspect ratio?
Fix one side and derive the other: new height = new width x old height / old width. Then round to an even number. Scaling 1920 x 1080 to a width of 1000 gives a height of 562.5, which rounds down to 562. In ffmpeg the scale filter does this for you when you give one dimension as -2, which the ffmpeg documentation describes as keeping the ratio with a size divisible by 2.
Why does my video need an even width and height?
H.264 uploads use 4:2:0 chroma subsampling, and YouTube Help lists exactly that for H.264 (checked October 2026). In 4:2:0 the colour information is stored at half the width and half the height of the picture, so an odd size has no clean half. Our explanation, not a quote: encoders such as libx264 commonly reject odd sizes for that reason, which is why this calculator never returns one.
How do I convert 16:9 to 9:16 without stretching?
You cannot fit a landscape frame into a vertical one without losing something, so there are only two honest options. Crop keeps the full height and cuts a centred 9:16 slice from the middle, so the sides are lost. Pad keeps the whole frame and adds bars above and below. Stretching distorts people and circles and is never the right answer. For 1920 x 1080 the crop window is 606 x 1080.
Should I crop or pad when making a vertical video?
Crop when the subject sits in the middle and the edges are expendable, because the picture fills the whole vertical screen. Pad when the whole frame matters, such as a screen recording, a slide or a wide shot, because nothing is cut. This is our advice, not a platform rule. If the subject moves around the frame, a fixed centred crop will cut them off, and you need to move the crop window over time instead.
What is the aspect ratio of 1920x1080, 3840x2160 and 1080x1920?
1920 x 1080 and 3840 x 2160 are both 16:9. 1080 x 1920 is 9:16, the same shape turned on its side. 1080 x 1080 is 1:1, and 1080 x 1350 is 4:5. The ratio only tells you the shape; it says nothing about how many pixels there are, so 1920 x 1080 and 3840 x 2160 share a shape at different sizes.
Is my video uploaded when I use this calculator?
No. The calculator never asks for a video file. It is arithmetic on the numbers you type, it runs in your browser, and nothing is sent to Linkeddit or anywhere else.
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