Aspect ratio

How the numbers are made

An aspect ratio is width divided by height, written in lowest whole numbers. 1920 by 1080 divides by 120, which leaves 16:9. 1080 by 1920 divides by 120 and leaves 9:16. 1080 by 1350 divides by 270 and leaves 4:5. The same shape at another size is the same ratio, so 1280 by 720 is also 16:9. The decimal on this page is width divided by height: 16:9 prints as 1.778:1, and 9:16 prints as 0.563:1.

To find a missing side, multiply the side you know by the other half of the ratio. Height equals width times ratio height divided by ratio width. A 16:9 frame at 1920 wide is 1920 times 9 divided by 16, which is 1080. A 9:16 frame at 1080 wide is 1080 times 16 divided by 9, which is 1920. Encoders that use 4:2:0 color want both sides even. This page rounds a crop or a fitted picture to the nearest even pixel that still fits, then splits the leftover pixels so the two edges add up to the exact remainder. One edge can be a pixel larger than the other. When that even size is not a perfect ratio, the result says so.

Crop window and delivery size

Two different sizes show up when a 16:9 frame has to become 9:16. The crop window is the part of the source you keep. For 1920 by 1080 into 9:16, the even crop is 608 by 1080, which drops 656 pixels from the left and 656 from the right. That window is about a third of the source. A perfect 9:16 at a height of 1080 would be 607.5 pixels wide, and 607.5 is not a whole pixel, so the page uses 608.

The delivery size is a whole frame at the target ratio. With the short side at 1080, 9:16 is 1080 by 1920. Those two numbers are not interchangeable. Paste the crop window into a crop. Paste the delivery size into the sequence or the export. The ladder also lists even frames whose short side is 720, 1440, or 2160 when both sides come out even.

Contain keeps every source pixel and adds bars. The same 1920 by 1080 fitted inside 1080 by 1920 scales to 1080 by 608, with 656 pixels of bar above and 656 below. The picture fills about a third of that tall frame. The YouTube help page opened on 2026-10-17 says the player can pad a shape that is not 16:9, and it says to leave that padding out of the file. The bar sizes here are the arithmetic. They are not an instruction to export black bars for a YouTube upload. An ffmpeg scale and pad line is a copy button for an editor that wants the same numbers. This page does not run it.

What the platform pages say

The YouTube resolution help page opened on 2026-10-17 says the standard aspect ratio on a computer is 16:9. Encode targets named there include 720p at 1280 by 720, 1080p at 1920 by 1080, and 4K at 3840 by 2160. A 2560 by 1440 row in the ladder is even arithmetic at 16:9. It is not labeled here as one of those named targets.

The three-minute Shorts help page, read the same day, says a square or vertical video up to three minutes, uploaded to a standard channel on or after 15 October 2024, is categorized as a Short. A wider ratio such as 16:9 is how that page says you keep a video off that shelf. That page did not print 1080 by 1920 as a required size. This calculator will still compute 1080 by 1920 as an even 9:16 frame. It does not call that pair a YouTube requirement. Official Artist Channels use 8 December 2025 as the matching date on the Shorts page of this directory. That date is not a second formula.

TikTok workflows on this directory use a 9:16 timeline. A TikTok-published minimum resolution, a maximum duration, and a file-size cap were not observed on the pass that wrote the TikTok page. This calculator does not invent them. Feed portrait 4:5 is a common feed shape. It is not a size copied from a Shorts or TikTok help page. Square 1:1 is an even shape the Shorts page includes when it says square or vertical.

Models, and the file you drop

Asking a model for a vertical frame and cropping a horizontal generation are different jobs. On the model pages checked 2026-10-16, Veo lists 16:9 and 9:16. Kling's fal Pro card lists 16:9, 9:16, and 1:1. Seedance's fal US text-to-video card lists auto, 21:9, 16:9, 4:3, 1:1, 3:4, and 9:16. The image-to-video extract used for that page did not restate the enum. Luma Ray and Higgsfield Cinema list a set that includes 21:9 and 9:16. Runway Gen-4.5 did not print an aspect enum on the price guide read that day, so this page does not claim a ratio for it. A model that can be asked for 9:16 still does not compose the shot. Cropping a 16:9 generation keeps a center strip and drops the sides.

A file you drop here is read in this tab. Width, height, and, for a video, duration come from the browser. The file is not uploaded, and this page does not export a new picture or a new video. If the browser cannot read the file, type the numbers. The opening 1920 by 1080 is a sample 16:9 frame so the result is not blank. Replace it with the frame you have. The usual finish for a vertical cut on this directory is a 9:16 timeline in CapCut, including the long-to-short path, and then captions. This page only supplies the numbers for that reframe.

How do I calculate an aspect ratio?

Divide the width and the height by their greatest common divisor. 1920 and 1080 divide by 120 to give 16:9. The missing side of a locked ratio is the side you know times the other ratio number divided by the ratio number you matched. 1920 wide at 16:9 is 1080 tall.

What size is a YouTube video?

The help page opened on 2026-10-17 says the standard on a computer is 16:9 and names encode targets that include 1920 by 1080, 1280 by 720, and 3840 by 2160. It says to leave padding out of the file.

Does a vertical upload become a Short?

The Shorts help page opened on 2026-10-17 says a square or vertical video up to three minutes, on a standard channel, uploaded on or after 15 October 2024, is categorized as a Short. A wider ratio such as 16:9 is how that page says a video stays off the shelf. Enter a duration here before that length rule is applied. A required pixel size was not on that page.

Should I crop or add bars?

Crop when the subject can live in the center of the new frame. Add bars when the edges have to stay. For YouTube, the help page says to leave padding out of the file and let the player add it. The crop window and the delivery size are different numbers. Copy the one the editor is asking for.

Which models list 9:16?

On the cards checked 2026-10-16, Veo, Kling, Seedance on the fal US text-to-video card, Luma Ray, and Higgsfield Cinema list 9:16. Runway Gen-4.5 did not print an aspect list on the price guide. Not observed there. 4:5 was not on those cards. Seedance's image-to-video extract did not restate the text-to-video enum.

Does this page upload my video?

No. The file is read in the browser for width, height, and duration. It is not uploaded. The page does not render a cropped file. Copy the numbers into the editor you already use.