Video Aspect Ratios Explained: 16:9, 9:16, 1:1 and 4:5

Aspect ratio is the proportion between a video’s width and its height. It is written as two numbers separated by a colon, and it describes shape rather than size. A 16:9 video is sixteen units wide for every nine tall, whether that is 1280×720 or 3840×2160.

The ratios you will meet

16:9 (landscape) is the standard for television, monitors, YouTube and most cameras. If you have not deliberately chosen otherwise, you shot in 16:9.

9:16 (vertical) is 16:9 rotated. It fills a phone screen held normally, which is why short-form video on TikTok, Reels and Shorts uses it.

1:1 (square) is a compromise that reads acceptably in both orientations. It was popularised by early Instagram and still appears in feed video.

4:5 (portrait) is taller than square but not full vertical. It occupies more feed height than 1:1 without committing to full-screen vertical, which is why it is common for feed posts as opposed to stories.

What happens when the ratio does not match

When a 16:9 video is played in a 9:16 space, something has to give, and there are only three options.

Letterboxing keeps the whole frame and adds bars to fill the space. Nothing is lost, but on a vertical feed a landscape video becomes a small strip with large empty regions, which looks unconsidered and performs poorly.

Cropping fills the space by discarding the edges. The video looks native, but you lose real content. A two-person interview shot in 16:9 will lose one of them when cropped to 9:16.

Stretching distorts the image to fit. It always looks wrong and no platform does it deliberately.

Platforms make this choice for you when your upload does not match, and they are not clever about it. Automatic cropping takes the centre, which is frequently not where the subject is.

Shoot for the destination

The reliable approach is to record in the ratio you intend to publish in. If the video is for a vertical feed, hold the phone vertically.

When one piece of footage must serve several destinations, shoot 16:9 but compose with margin: keep the important action inside the central vertical band so a 9:16 or 1:1 crop still contains the subject. Camera apps often offer a framing guide for this.

Resolution is a separate question

Aspect ratio is shape; resolution is pixel count. 1920×1080 and 1280×720 are both 16:9. Changing resolution while keeping the ratio scales the image with no cropping. Changing the ratio necessarily crops, pads or distorts.

This matters when a platform states a maximum resolution. Reducing 4K to 1080p in the same ratio loses no framing at all.

A note on what platforms do to your upload

Every major platform re-encodes what you upload, to their own codec, bitrate and often resolution. You are giving them a source to work from, not a final file.

The practical consequences: upload in the correct aspect ratio, because that is the decision they cannot reverse; do not spend effort matching an exact bitrate, because it will be discarded; and upload at a good quality level, since re-encoding an already heavily compressed file compounds the damage.

Correct shape, generous quality, and let the platform do the rest.