Aspect Ratio Calculator for Video
Calculate video aspect ratios and resize dimensions without stretching. Find the missing width or height for 16:9, 9:16, 4:3, 1:1, 21:9 and custom ratios.
Common video aspect ratios
| Ratio | Typical sizes | Used for |
|---|---|---|
| 16:9 | 1280×720, 1920×1080, 3840×2160 | YouTube, TV, streaming services, presentations |
| 9:16 | 1080×1920 | TikTok, Instagram Reels, YouTube Shorts, Stories |
| 1:1 | 1080×1080 | Feed posts, ads |
| 4:5 | 1080×1350 | Instagram and Facebook feed portrait |
| 4:3 | 640×480, 1440×1080 | Older TV, some tablets and webcams |
| 21:9 / 2.39:1 | 2560×1080, 3840×1607 | Cinematic films, ultrawide monitors |
How to use the calculator
Pick a preset or type your own ratio. Then change either the width or the height and the other value updates to match. Results are rounded to even numbers because most video codecs need them. The preview box shows the shape at a glance.
Avoiding stretching and black bars
If your source and target ratios differ, you have three choices: letterbox (add bars), crop (cut the edges) or stretch (distort). Stretching almost always looks wrong. For social clips, crop and reframe the subject. For streaming ladders, keep the source ratio for every rendition, so a 1920×1080 master becomes 1280×720, 960×540 and 640×360. Our encoding settings guide has a complete ladder.
Frequently asked questions
What is the aspect ratio of 1920×1080?
1920×1080 is 16:9, the standard widescreen ratio used by HD and 4K television, YouTube and most monitors.
What aspect ratio should I use for Reels, TikTok and Shorts?
Use 9:16 vertical video, usually at 1080×1920 pixels.
Why should dimensions be even numbers?
H.264 and HEVC encoders using 4:2:0 chroma subsampling need even width and height. Odd numbers cause errors or a padded line.