Creator media glossary
What is aspect ratio?
Short answer
The proportional relationship between a video or image's width and height, written as two numbers like 9:16 or 16:9.
Key takeaways
- Aspect ratio is the shape of a frame: width to height, such as 16:9 or 9:16.
- TikTok, Reels, Shorts and stories are 9:16; YouTube is 16:9; feed posts work best at 4:5.
- It is not resolution: 1080 × 1920 and 720 × 1280 are both 9:16.
- Change it by cropping or padding, never by stretching.
Aspect ratio explained
Aspect ratio describes shape, not size - a 9:16 video is "tall" whether it's 1080×1920 or 540×960. Every short-form platform is built around one primary shape: 9:16 for TikTok, Reels and Shorts; 16:9 for widescreen; 1:1 or 4:5 for feed posts.
Posting the wrong ratio doesn't just look odd - most platforms crop or letterbox it, cutting off the left and right sides of a landscape video cropped to fill a vertical feed, or adding bars around a square video in a widescreen player.
How to calculate an aspect ratio
- Divide width and height by their greatest common divisor: 1920 × 1080 ÷ 120 = 16:9; 1080 × 1350 ÷ 270 = 4:5.
- Or divide width by height: 1.78 means 16:9, 1.0 is square, 0.8 is 4:5, 0.5625 is 9:16. Cinema ratios are written this way (1.85:1, 2.39:1).
- To find a missing side, multiply: height = width × 9 ÷ 16 for 16:9, so 1280 wide is 720 high.
- Some sizes do not reduce neatly: 2560 × 1080 is 64:27, marketed as 21:9.
A short history of aspect ratios
- About 4:3 (1.33:1): early cinema, then television for most of the 20th century.
- 1.375:1, the Academy ratio, set in 1932 to make room for the optical soundtrack.
- 1.85:1 and 2.35:1 (now 2.39:1): widescreen formats such as CinemaScope, introduced in the 1950s as cinema competed with TV.
- 16:9 (1.78:1): proposed for HDTV in the 1980s as a compromise between 4:3 and the wide cinema ratios; now standard for TVs, laptops and YouTube.
- 9:16: phone-first vertical video, made mainstream by Snapchat Stories, TikTok, Reels and Shorts.
Common aspect ratios
| Ratio | Shape | Typical size | Where it is used |
|---|---|---|---|
| 9:16 | Tall | 1080 × 1920 | TikTok, Reels, Shorts, stories |
| 16:9 | Wide | 1920 × 1080 | YouTube, TV, laptop screens |
| 4:5 | Portrait | 1080 × 1350 | Instagram and Facebook feed |
| 3:4 | Portrait | 1080 × 1440 | Tallest uncropped Instagram feed photo |
| 1:1 | Square | 1080 × 1080 | Feed posts, profile pictures |
| 2:3 | Portrait | 1000 × 1500 | Pinterest pins |
| 1.91:1 | Wide | 1200 × 627 | Link previews (LinkedIn, Facebook) |
What happens to the wrong ratio
Platforms either crop the frame to their shape or add bars. Instagram crops feed photos outside 1.91:1-3:4 to the nearest supported ratio; Pinterest warns that pins taller than 2:3 may be cut off in feeds.
Reframe before you upload rather than letting the platform crop from the center, which tends to cut off text and faces at the edges.
Common sizes for each ratio
| Ratio | HD size | 4K size | Decimal |
|---|---|---|---|
| 16:9 | 1920 × 1080 | 3840 × 2160 | 1.78 |
| 9:16 | 1080 × 1920 | 2160 × 3840 | 0.56 |
| 4:5 | 1080 × 1350 | 2160 × 2700 | 0.8 |
| 1:1 | 1080 × 1080 | 2160 × 2160 | 1.0 |
| 4:3 | 1440 × 1080 | 2880 × 2160 | 1.33 |
| 21:9 (64:27) | 2560 × 1080 | 5120 × 2160 | 2.37 |
Aspect ratios beyond social media
| Ratio | Where you see it |
|---|---|
| 3:2 | Full-frame and APS-C cameras, 4 × 6 inch prints |
| 4:3 | Phone photos, iPads, Micro Four Thirds cameras |
| 5:4 | 8 × 10 inch prints, large-format photography |
| 16:10 | MacBooks and many laptops (1920 × 1200, 2560 × 1600) |
| 21:9 | Ultrawide monitors (2560 × 1080, 3440 × 1440) |
| 19.5:9 and 20:9 | Modern phone screens |
| 2.39:1 | Widescreen cinema, the "letterboxed" look |
How to change an aspect ratio
- Crop: cut the frame to the new shape. Nothing is distorted, but you lose the edges, so place the subject first.
- Pad (letterbox or pillarbox): add bars or a blurred copy of the video to fill the new shape. Nothing is lost, but the picture is smaller.
- Reframe: crop with a moving window that follows the subject; editors call it auto reframe or smart crop.
- Never stretch: changing the shape by scaling width and height differently distorts faces and text.
- Our aspect ratio tools crop video and images to 9:16, 1:1, 4:5, 16:9, 4:3 and 21:9 in the browser.
Free tools:Crop video to 9:16Crop an image to 4:5All aspect ratios
Pixel aspect ratio
Usually pixels are square, so the frame shape and the pixel count agree. Some older and professional formats use non-square pixels: NTSC DV stores 720 × 480 but displays as 4:3 or 16:9, and anamorphic lenses squeeze a wide image onto a narrower sensor. If a video looks squashed after import, the pixel aspect ratio was read wrongly; set it in the clip's properties.
Frequently asked questions
What does aspect ratio mean?
Aspect ratio is the shape of an image or video: its width divided by its height, written as two numbers such as 16:9 (wide) or 9:16 (tall). It says nothing about size: 1080×1920 and 720×1280 are both 9:16.
What aspect ratio is best for Instagram?
Reels and stories: 9:16, which the Instagram API recommends to avoid cropping or blank space. Feed photos: Instagram keeps anything from 1.91:1 to 3:4 uncropped, so 4:5 or 3:4 portrait fills the most screen.
What aspect ratio does YouTube use?
YouTube says the standard aspect ratio on a computer is 16:9, and that the player adapts automatically to vertical and square videos. Shorts are vertical.
How do I work out an aspect ratio?
Divide width and height by their greatest common divisor: 1920×1080 ÷ 120 = 16:9. Or divide width by height (1.78 for 16:9, 0.5625 for 9:16) and compare.
Is 1080p an aspect ratio?
No, it is a resolution. 1920 × 1080 has a 16:9 aspect ratio; 1080 × 1920 is the same resolution turned vertical, 9:16.
What aspect ratio is a phone screen?
Most modern phones are about 19.5:9 or 20:9, taller than 16:9. Vertical 9:16 video fills most of the screen; apps place their buttons over the extra space.
Let Koldflux pick the settings
Koldflux chooses the codec, container and bitrate for each platform when it exports.
Free tools that use this
Sources and how we checked
- Instagram API: IG User Media (reel, story and video specifications) (checked 2026-10-05)
- Instagram Help: Image resolution of photos you share (checked 2026-10-05)
- YouTube Help: Recommended upload encoding settings (checked 2026-10-05)
- Pinterest Help: Pinterest product specs (checked 2026-10-05)
- LinkedIn Help: Image specifications for LinkedIn Pages (checked 2026-10-05)
Reviewed October 5, 2026 by the Koldflux team. Definitions follow the specifications and platform documentation linked above; platform tables come from the same registry the Koldflux tools use.