Aspect Ratio Calculator
Calculate aspect ratios from dimensions. Find width or height from a ratio. Platform presets for YouTube, Instagram, TikTok.
| Platform | Resolution | Aspect ratio | Match |
|---|---|---|---|
| YouTube | 1920×1080 | 16:9 | — |
| YouTube | 1280×720 | 16:9 | — |
| YouTube | 3840×2160 | 16:9 | — |
| Instagram Feed | 1080×1080 | 1:1 | — |
| Instagram Feed | 1080×1350 | 4:5 | — |
| Instagram Story / TikTok | 1080×1920 | 9:16 | — |
| 1200×675 | 16:9 | — | |
| 1200×630 | 1.91:1 | — |
What is Aspect Ratio Calculator?
An aspect ratio is the proportional relationship between the width and height of an image or video. It's expressed as width:height—for example, 16:9 for widescreen or 1:1 for square. The aspect ratio defines the shape regardless of absolute size: a 1920×1080 display and a 1280×720 video both have the same 16:9 ratio.
Common ratios include 16:9 (widescreen TV, YouTube, streaming), 4:3 (older TVs and monitors), 1:1 (square, used for Instagram feed), 9:16 (portrait video for Stories, Reels, TikTok), 21:9 (ultrawide monitors), and 3:2 (many cameras and photos). This tool calculates the simplified ratio from any dimensions, shows the decimal value, and lets you lock the ratio to scale one dimension while the other adjusts automatically.
How to Use Aspect Ratio Calculator
- Enter Width and Height in the input fields. The ratio, decimal value, and preview update as you type.
- Click a preset chip (16:9, 4:3, 1:1, 21:9, 9:16, 3:2) to instantly set common aspect ratios with standard dimensions.
- Enable Lock ratio to maintain the current aspect ratio. When locked, changing width recalculates height (and vice versa) so the ratio stays constant.
- Use Swap W/H to exchange width and height—useful for converting between landscape and portrait. Use Clear to reset to defaults.
- Check the platform presets table to see standard resolutions for YouTube, Instagram, TikTok, Twitter, and Facebook, with a Match column showing which platforms match your current ratio.
Tips & Best Practices
For YouTube, use 16:9 (1920×1080 or higher). For Instagram Feed, 1:1 (1080×1080) or 4:5 (1080×1350) work best. For Stories, Reels, and TikTok, use 9:16 (1080×1920). Twitter and Facebook prefer 16:9 for video and 1.91:1 (1200×630) for link preview images. Always export at the target platform's recommended resolution to avoid cropping or letterboxing. The visual preview helps you see the shape at a glance. Press Esc to clear.
When to Use This Tool
Use the Aspect Ratio Calculator when editing video for different platforms, sizing responsive images, designing social media graphics, or ensuring consistent proportions across screens. It's ideal for video editors, designers, and content creators who need to match YouTube, Instagram, TikTok, or other platform specs. Pair it with our Image Resizer to resize images to exact dimensions, or the CSS Unit Converter when working with responsive layout units.
Frequently Asked Questions
What is an aspect ratio?
An aspect ratio is the proportional relationship between width and height of an image or video, expressed as width:height (e.g. 16:9). It describes the shape regardless of absolute size.
What is the most common aspect ratio?
16:9 is the most common aspect ratio for video and displays today—used for widescreen TV, YouTube, and most streaming content. 4:3 was standard for older TVs and monitors.
What aspect ratio is 1920×1080?
1920×1080 simplifies to 16:9. Both dimensions divide by 120: 1920÷120=16, 1080÷120=9. It's the standard Full HD resolution for widescreen video.
How do I calculate aspect ratio from dimensions?
Divide width by height to get the decimal ratio. To get the simplified ratio (e.g. 16:9), find the GCD of width and height, then divide both by it. Example: 1920 and 1080 have GCD 120, so 1920:1080 = 16:9.
What aspect ratio should I use for social media?
Use 1:1 for Instagram feed squares, 4:5 (1080×1350) for portrait feed posts, and 9:16 for Stories, Reels, and TikTok. Twitter and Facebook prefer 16:9 or 1.91:1 (1200×630) for link previews.
What is the difference between 16:9 and 4:3?
16:9 is wider (1.78:1) and used for widescreen TV, YouTube, and modern displays. 4:3 is narrower (1.33:1) and was the standard for older CRT TVs and monitors. 16:9 shows more horizontal content; 4:3 has a more square shape.