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How to Use
- 1To find the ratio: enter width and height in pixels and click Calculate Ratio.
- 2To find a dimension: switch to the 'Dimension from Ratio' tab.
- 3Select a preset ratio (16:9, 4:3, etc.) or enter a custom ratio.
- 4Enter the known dimension and select whether it is the width or height.
- 5Click Calculate to get the missing dimension.
About Aspect Ratio Calculator
The Aspect Ratio Calculator has two modes: calculate the simplified ratio from any two dimensions (e.g., 1920×1080 → 16:9), or find a missing dimension when you know the ratio and one side. GCD-based simplification ensures accurate ratio detection.
Includes presets for the most common ratios: 16:9 (HD video, YouTube), 4:3 (presentations), 1:1 (Instagram square), 9:16 (Stories, Reels, TikTok), 21:9 (ultrawide), and more. Select a preset and enter one dimension to instantly calculate the other.
Video editors, graphic designers, web developers, and social media managers rely on this tool to calculate image crops, video exports, responsive container sizes, and thumbnail dimensions without manual math.
Frequently Asked Questions
What is an aspect ratio?
An aspect ratio is the proportional relationship between width and height, expressed as W:H (e.g., 16:9). It describes the shape of an image or screen regardless of its actual pixel size.
What ratio is 1920×1080?
1920×1080 is a 16:9 aspect ratio — the standard for Full HD video, YouTube uploads, and most modern monitors and TVs.
Which ratio should I use for Instagram?
Instagram supports 1:1 (square posts), 4:5 (portrait feed posts), and 1.91:1 (landscape). Stories and Reels use 9:16 (1080×1920).
How does ratio simplification work?
The tool divides both dimensions by their greatest common divisor (GCD) to produce the simplest integer ratio. For example, 3840×2160 simplifies to 16:9.
What ratio is best for YouTube thumbnails?
YouTube thumbnails use 16:9 at 1280×720 pixels. This ratio matches the video player and prevents black bars or cropping.