Aspect Ratios Explained: 16:9, 9:16, 4:5 and 1:1
What aspect ratio means, which one to use for YouTube, Reels, TikTok and Instagram, how to calculate it, and how to fix a video with black bars.
Quick answer: use 16:9 for YouTube and TV, 9:16 for Reels, TikTok, Shorts and Stories, 4:5 for Instagram portrait posts, and 1:1 for square posts. You can work out any size with the Aspect Ratio Calculator.
What is an aspect ratio?
It is the shape of a picture: width compared to height. A 1920 × 1080 video is 16 : 9 because 1920 ÷ 120 = 16 and 1080 ÷ 120 = 9. Size and shape are different things: 1280 × 720 and 3840 × 2160 are both 16:9.
Which ratio for which platform?
| Ratio | Shape | Use it for |
|---|---|---|
| 16:9 | Wide | YouTube videos, TV, laptop screens |
| 9:16 | Tall | Reels, TikTok, YouTube Shorts, Stories, WhatsApp Status |
| 4:5 | Slightly tall | Instagram portrait posts (the most screen space in the feed) |
| 1:1 | Square | Classic Instagram and Facebook posts, profile photos |
| 3:2 | Wide | Camera photos |
| 21:9 | Very wide | Cinema and ultrawide monitors |
How to calculate it yourself
Find the ratio: divide both numbers by their greatest common divisor. 1080 × 1350: both divide by 270, which gives 4 : 5.
Find a missing side: height = width × (ratio height ÷ ratio width). For a 9:16 video that is 1080 wide: 1080 × 16 ÷ 9 = 1920 tall.
Or just type the numbers into the Aspect Ratio Calculator.
Why do I get black bars?
Black bars appear when a video's shape doesn't match the screen's:
- A wide 16:9 video on a phone held upright gets bars above and below.
- A vertical 9:16 video on a TV gets bars at the sides.
To avoid them, shoot or export in the shape of the place you will post.
How to change the shape of a photo
- Cut parts off: use the Image Cropper and choose a ratio.
- Keep everything: use the Image Resizer with a preset and Fit, which adds borders instead of cutting.
- For the exact pixels for each app, see Social media image & video sizes 2026.
Does the ratio change the file size?
Indirectly, because more pixels mean a bigger file. To estimate a video's size from its quality and length, use the Video File Size Calculator.
Work out any size: Aspect Ratio Calculator →