Aspect Ratio Calculator

1. Select a mode: calculate ratio from dimensions, resize keeping ratio, or browse common presets.
2. Enter your width and height values in the input fields.
3. The simplified aspect ratio or resized dimension is calculated automatically.
4. Click the copy button to copy any result to your clipboard.

What is an Aspect Ratio?

An aspect ratio describes the proportional relationship between the width and height of an image, screen, or video frame. It is expressed as two numbers separated by a colon, such as 16:9 or 4:3, where the first number represents the width and the second represents the height. Aspect ratios are fundamental in display technology, photography, videography, web design, and print media. This tool uses the greatest common divisor (GCD) algorithm to simplify pixel dimensions into their cleanest ratio form, and can proportionally resize dimensions to maintain original proportions.

How It Works

To calculate an aspect ratio from pixel dimensions, the tool finds the greatest common divisor of the width and height, then divides both values by it. For example, 1920x1080 has a GCD of 120, so 1920/120 = 16 and 1080/120 = 9, yielding the ratio 16:9. For proportional resizing, when you change one dimension, the tool calculates the other by maintaining the same ratio: new height = new width * (original height / original width). This ensures images are never stretched or squished when resized.

Common Aspect Ratios

• 16:9 - Standard widescreen (1920x1080, 2560x1440, 3840x2160)
• 4:3 - Traditional TV and iPad displays (1024x768, 2048x1536)
• 1:1 - Square format (Instagram posts, profile pictures)
• 21:9 - Ultrawide monitors and cinematic displays
• 9:16 - Vertical video (Stories, Reels, TikTok)
• 3:2 - Many DSLR cameras and some laptops (Surface devices)

Aspect Ratios in Web Design

In responsive web design, maintaining aspect ratios prevents layout shifts when images load. CSS provides the aspect-ratio property to enforce specific proportions on elements. Video embeds (YouTube, Vimeo) typically use 16:9, so setting a container with aspect-ratio: 16/9 reserves the correct space before the video loads. Hero images and banner ads have specific aspect ratio requirements that vary by platform. Understanding aspect ratios also matters for CSS object-fit decisions: whether to crop, contain, or stretch an image to fill a container.

For resizing images while maintaining proportions, use the Image Resizer. For percentage calculations, try the Percentage Calculator.