Free Aspect Ratio Calculator
Calculate and convert aspect ratios for video and images. Presets for YouTube, TikTok, Instagram, and more. No signup required.
Simplified: 16:9 · Decimal: 1.778
Visual Preview
16:9 (1.778)
2.07 MP
What Is an Aspect Ratio Calculator?
An aspect ratio calculator helps you determine the correct width and height dimensions for images and videos while maintaining a specific proportional relationship. The aspect ratio is the proportional relationship between width and height — 16:9 means for every 16 units of width, there are 9 units of height. This is critical for video and image production because using the wrong ratio causes black bars (letterboxing/pillarboxing), cropping, or stretching on different platforms and screens. YouTube standard videos use 16:9, YouTube Shorts and TikTok use 9:16 (vertical), Instagram feed posts use 1:1 (square) or 4:5 (portrait), and cinema uses 2.39:1 (ultra-widescreen). Our free calculator lets you enter any ratio and one dimension (width or height) to instantly calculate the other dimension, with visual previews and one-click copy of the results.
How Does the Aspect Ratio Calculator Work?
The math is straightforward but the tool handles all edge cases and formatting for you. Given an aspect ratio of W:H and a target width, the height is calculated as: height = (targetWidth × H) / W, rounded to the nearest even number (important for video codecs that require even dimensions). Given a target height, width is calculated as: width = (targetHeight × W) / H. The tool also performs GCD (Greatest Common Divisor) reduction to simplify any custom ratio you enter — so if you enter 1920:1080, it shows you that's equivalent to 16:9. The visual preview scales a rectangle to match your calculated ratio, letting you see the proportions at a glance. Preset buttons for common platform requirements (YouTube 1920×1080, TikTok 1080×1920, Instagram 1080×1080, etc.) let you get the right dimensions with a single click.
Features
- ✓Calculate width or height from any aspect ratio
- ✓Common presets for YouTube, TikTok, Instagram, cinema formats
- ✓Visual preview of the calculated dimensions
- ✓Pixel-perfect rounding for exact dimensions
- ✓Compare multiple ratios side by side
- ✓Copy dimensions in multiple formats (WxH, CSS, JSON)
Benefits
Pixel-Perfect Dimensions for Any Platform
Each platform has specific recommended dimensions. YouTube wants 1920×1080 (16:9), TikTok wants 1080×1920 (9:16), Instagram feed is 1080×1080 (1:1) or 1080×1350 (4:5). The calculator gives you exact pixel dimensions with proper rounding for video codec compatibility.
Prevent Cropping, Letterboxing, and Stretching
Uploading content with the wrong aspect ratio results in black bars, unwanted cropping, or distorted stretching. The calculator ensures your dimensions match the target platform's requirements exactly, preserving your visual composition.
Custom Ratios for Any Use Case
Beyond social media presets, the calculator handles any custom ratio — cinema formats (2.39:1), ultra-wide monitors (21:9), print sizes (3:2, 5:4), or any arbitrary proportion. Enter any ratio and get precise pixel dimensions.
Copy-Ready Output Formats
Copy your calculated dimensions as WxH (1920x1080), CSS properties (width: 1920px; height: 1080px), or JSON — ready to paste directly into your design software, code, or export settings.
Frequently Asked Questions
What aspect ratio is YouTube?
Standard YouTube videos use 16:9 (recommended resolution: 1920×1080 for 1080p, 3840×2160 for 4K). YouTube Shorts use 9:16 (recommended: 1080×1920). YouTube also supports other ratios but will add black bars (letterboxing) to maintain 16:9 for standard videos.
What aspect ratio is TikTok?
TikTok uses 9:16 vertical format. The recommended resolution is 1080×1920 pixels. While TikTok can display other ratios, 9:16 fills the entire screen and performs best in the algorithm. Videos wider than 9:16 will have black bars above and below.
What aspect ratio is Instagram?
Instagram supports multiple ratios: Feed posts use 1:1 (1080×1080 square) or 4:5 (1080×1350 portrait — shows largest in feed). Stories and Reels use 9:16 (1080×1920). Landscape posts use 1.91:1 (1080×566). The 4:5 portrait ratio takes up the most screen space in the feed.
Why do video dimensions need to be even numbers?
Most video codecs (H.264, H.265, VP9) process pixels in 2×2 blocks called macroblocks. Odd pixel dimensions cause encoding errors or quality loss at the edges. The calculator automatically rounds to even numbers to ensure codec compatibility.
How do I calculate aspect ratio from dimensions?
Divide both width and height by their Greatest Common Divisor (GCD). For example, 1920÷120 = 16 and 1080÷120 = 9, so 1920×1080 is 16:9. Our calculator performs this reduction automatically when you enter custom dimensions.
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