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Aspect Ratio Calculator
Calculate and simplify aspect ratios. Scale dimensions proportionally. Common presets for 16:9, 4:3, 21:9 and more. Free, private. 100% free, private,.
How to use
Enter Dimensions — Type width and height, or click a common preset
See Ratio — The simplified aspect ratio is calculated automatically
Scale — Enter a new width or height to get the proportional other dimension
What Is Aspect Ratio?
Aspect ratio is the proportional relationship between the width and height of an image, screen, or video. It's expressed as two numbers separated by a colon (e.g., 16:9) representing the simplified ratio of width to height. A 1920×1080 display has a 16:9 aspect ratio because 1920/120 = 16 and 1080/120 = 9.
Common Aspect Ratios
16:9 (1.78:1): The standard for HD and 4K displays, YouTube videos, and modern presentations. Resolutions: 1920×1080, 2560×1440, 3840×2160.
4:3 (1.33:1): The classic TV and monitor ratio. Still used for some presentations, iPads, and legacy content. Resolutions: 1024×768, 1600×1200.
21:9 (2.33:1): Ultrawide monitors and some cinema formats. Provides a panoramic viewing experience. Resolutions: 2560×1080, 3440×1440.
1:1: Square format, popular on Instagram and social media. Resolution: 1080×1080.
9:16: Vertical video for TikTok, Instagram Reels, and YouTube Shorts. Resolution: 1080×1920.
3:2 (1.5:1): Common in photography (35mm film), some Microsoft Surface devices, and Macbook displays.
Why Aspect Ratio Matters
Video production: Shooting in the wrong ratio means black bars or cropped content when displayed
Web design: Images must maintain proportions when displayed at different sizes
Social media: Each platform has preferred ratios (Instagram feed: 1:1 or 4:5, Stories: 9:16)
Print design: Photos must match print dimensions to avoid cropping or distortion
Display shopping: Understanding ratio helps compare monitors and TVs
Scaling While Maintaining Ratio
To resize an image or video while maintaining its aspect ratio, you only need to specify one dimension (width or height). The other is calculated automatically: New Height = New Width × (Original Height / Original Width). This prevents stretching or squishing.
Aspect Ratio in CSS
Modern CSS supports the aspect-ratio property: aspect-ratio: 16 / 9;. This makes responsive design easier by letting the browser calculate one dimension automatically based on the other and the specified ratio.
Privacy
All calculations run in your browser. No data is sent to any server.
An aspect ratio is the proportional relationship between width and height. 16:9 means for every 16 units of width, the height is 9 units. It's expressed as two numbers separated by a colon.
What is the most common aspect ratio?
16:9 (widescreen) is the most common for displays, videos, and presentations. 4:3 was the standard before widescreen adoption. 9:16 is standard for mobile/vertical video.
How do I maintain aspect ratio when resizing?
Enter your original dimensions to get the ratio, then enter either a new width or new height. The tool calculates the other dimension to maintain the same proportions.
What's the difference between 16:9 and 1.78:1?
They're the same ratio expressed differently. 16÷9 = 1.7778. The colon notation (16:9) is more common in consumer electronics; the decimal notation (1.78:1) is used in cinema.
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