Understanding Aspect Ratios: A Complete Guide

What Is Aspect Ratio?

Aspect ratio describes the shape of your video. It's the proportional relationship between width and height, expressed as two numbers separated by a colon.

A 16:9 video is 16 units wide for every 9 units tall. A 1:1 video has equal width and height. The actual pixel count doesn't matter for the ratio. A 1920×1080 video and a 1280×720 video are both 16:9 because they share the same proportions.

Think of aspect ratio like the shape of a picture frame. You can have a wide landscape frame, a tall portrait frame, or a square frame. The frame shape is the aspect ratio. The actual size of the frame is the resolution.

Why Does Aspect Ratio Matter?

Every screen and platform has an expected aspect ratio. When your video doesn't match, something has to give. Either black bars appear around your video, part of your video gets cut off, or your video looks stretched and distorted.

Getting the aspect ratio right means your video fills the available space properly. It looks intentional, professional, and takes up maximum screen real estate. Wrong aspect ratios make videos look like an afterthought.

Common Aspect Ratios Explained

16:9 (Widescreen)

The standard for computer monitors, TVs, and YouTube. This is what most people think of as "normal" video shape. It's wide and rectangular, matching the way we naturally see the world in a horizontal sweep.

Common resolutions: 1920×1080 (Full HD), 3840×2160 (4K), 1280×720 (HD)

Use for: YouTube videos, website backgrounds, TV content, presentations, most desktop viewing

9:16 (Vertical)

The same as 16:9, but flipped. This is phone-first video, designed for how people hold their phones most of the time. It dominates short-form content platforms.

Common resolutions: 1080×1920 (Full HD vertical), 720×1280 (HD vertical)

Use for: TikTok, Instagram Reels, YouTube Shorts, Instagram Stories, Snapchat

1:1 (Square)

Equal width and height. Squares work well in scrolling feeds because they take up significant vertical space without feeling as tall as vertical video. They also look good on both desktop and mobile.

Common resolutions: 1080×1080, 720×720

Use for: Instagram feed posts, some Twitter content, Facebook feed

4:5 (Vertical Rectangle)

Slightly taller than square but not as tall as 9:16. Instagram recommends this for feed posts because it takes up more screen space than square while still looking balanced. It's a good middle ground.

Common resolutions: 1080×1350, 864×1080

Use for: Instagram feed posts (optimal), Facebook feed

4:3 (Classic TV)

The shape of old televisions and early computer monitors. You'll mostly see this in older content, security cameras, and some professional video applications. It's boxy compared to modern widescreen.

Common resolutions: 1440×1080, 640×480

Use for: Vintage aesthetics, some professional applications

21:9 (Ultrawide/Cinematic)

Extra-wide format used in movies. Creates a cinematic letterboxed look. Most screens can't display this without black bars on top and bottom, which is actually part of the aesthetic.

Common resolutions: 2560×1080, 3440×1440

Use for: Cinematic content, ultrawide monitors, film trailers

Which Platforms Use Which Ratios

YouTube

Standard videos: 16:9 (1920×1080 recommended). YouTube Shorts: 9:16 (1080×1920). YouTube supports other ratios but will add black bars around them. For regular uploads, 16:9 fills the player perfectly.

TikTok

9:16 (1080×1920 recommended). TikTok is built for vertical video. Horizontal content technically works but looks out of place and wastes most of the screen.

Instagram

Reels and Stories: 9:16 (1080×1920). Feed posts: 1:1 (1080×1080) or 4:5 (1080×1350). The feed supports multiple ratios, but 4:5 takes up the most space while scrolling and often performs best.

LinkedIn

16:9 (1920×1080) or 1:1 (1080×1080). LinkedIn is flexible with ratios. Square works well for mobile feed viewing, while widescreen fits professional presentation content.

Twitter/X

16:9 (1280×720 recommended) or 1:1 (720×720). Twitter crops videos in the feed to roughly 16:9 regardless of original ratio, so plan your framing accordingly.

Facebook

Feed: 16:9 (1280×720) or 1:1 (1080×1080). Reels and Stories: 9:16 (1080×1920). Facebook is the most flexible platform for aspect ratios.

How to Calculate Aspect Ratio

To find a video's aspect ratio, divide both the width and height by their greatest common divisor. For 1920×1080, you can divide both by 120 to get 16:9. For 1080×1350, divide by 270 to get 4:5.

Or just remember the common pairs. If the numbers are similar (like 1080 and 1080), it's square. If width is much larger than height, it's widescreen. If height is much larger than width, it's vertical.

Converting Between Aspect Ratios

When your video is one ratio and you need another, you have three options:

Letterboxing (Adding Bars)

Scale your video to fit inside the new ratio and fill the remaining space with solid color (usually black). A 16:9 video letterboxed to 1:1 gets black bars on top and bottom. A 9:16 video letterboxed to 16:9 gets black bars on the sides (sometimes called pillarboxing).

Pros: Preserves all your content. Nothing gets cut off.

Cons: Black bars look dated and waste screen space. Some platforms penalize letterboxed content in their algorithms.

Cropping (Cutting Edges)

Cut off the parts of your video that don't fit the new ratio. A 16:9 video cropped to 1:1 loses the left and right edges. A 9:16 video cropped to 16:9 loses most of the top and bottom.

Pros: Clean, full-frame result. No wasted space.

Cons: You lose part of your image. Important content near the edges might get cut off.

Stretching (Distorting)

Force your video into the new ratio by squishing or stretching it. People and objects look wrong. Circles become ovals. This is almost never what you want.

Pros: Uses full frame, no content loss.

Cons: Everything looks distorted and unprofessional.

Practical Tips for Aspect Ratio

Plan your framing before recording. If you know you need vertical video, record vertically. If you need multiple ratios, frame your subject in the center with plenty of margin around them.

Record in high resolution. Starting with 4K gives you room to crop to different ratios while maintaining quality. A 4K 16:9 video can be cropped to a 1080p square without losing sharpness.

Use the center of the frame. Keep your subject and any text or graphics away from the edges. This gives you flexibility to crop for different platforms without losing anything important.

Test your output. After converting, check that text is readable, faces aren't cut off, and the video looks right on the intended platform.

Using VidStudio for Aspect Ratio Conversion

VidStudio's resize tool handles all aspect ratio conversions. Select a platform preset (YouTube, TikTok, Instagram, etc.) or enter custom dimensions. Choose between letterbox, crop, or stretch. The tool processes everything in your browser without uploading your files anywhere.

For batch processing multiple videos to the same aspect ratio, use the Normalize feature with canvas presets for vertical (9:16), square (1:1), or widescreen (16:9).

Frequently Asked Questions

What's the difference between aspect ratio and resolution?

Aspect ratio is the shape (proportional relationship of width to height). Resolution is the size (actual pixel count). A video can have the same aspect ratio at different resolutions. 1920×1080 and 1280×720 are both 16:9, but one has more pixels than the other.

Why does my vertical video have black bars on YouTube?

YouTube's player is widescreen (16:9). When you upload a 9:16 vertical video as a regular upload (not a Short), the player adds black bars on the sides to fill the space. Upload it as a YouTube Short instead, or accept the bars for regular uploads.

What's the best aspect ratio for Instagram?

For Reels and Stories: 9:16. For feed posts: 4:5 takes up the most space while scrolling and often gets better engagement than square. If you want one video for both, 9:16 works everywhere on Instagram.

Can I change aspect ratio without losing quality?

Letterboxing doesn't touch your actual video, so quality stays the same (you just add empty space). Cropping removes pixels but doesn't degrade the remaining image. Stretching technically preserves pixel count but distorts the image.

What if I don't know my video's aspect ratio?

Drop your video into VidStudio and the tool shows you the current dimensions. From there you can calculate the ratio or just pick your target preset and let the tool handle the conversion.