Aspect Ratio Calculator

Calculate aspect ratios, find missing image or video dimensions, and verify proportions for common formats like 16:9, 4:3, and 1:1.

Summary:An aspect ratio calculator determines proportional width and height dimensions for photography, video displays, and responsive web layouts, maintaining exact visual scaling without stretching or distortion.
Quick Preset Selection
Original Dimensions (Required)
Target Dimensions (Optional)
Original Dimensions
16:9

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How to Use Aspect Ratio Calculator

Follow these steps to use the Aspect Ratio Calculator: 1. Use the Ratio Finder tab to enter original and target dimensions and instantly see their simplified ratios and proportionality. 2. Use the Missing Dimension tab to calculate an unknown width or height from a known ratio. 3. Use the Preset Ratios tab to explore common ratios for video, photography, and social media. Enter your values to calculate the result instantly. This tool performs calculations locally in your browser.

Aspect Ratio Calculator Formula / How It Works

The calculator finds the Greatest Common Divisor (GCD) of the two input values using the Euclidean algorithm and divides both by it to produce the simplest whole-number ratio. Missing dimensions are found by multiplying the known dimension by the inverse ratio.

Formula:Ratio = Width:Height simplified by GCD; Missing Dimension = Known × (ratio side / other ratio side); Scale Factor = Target / Original
Example Calculation:

For example, let's look at entering 1920 × 1080 and a target of 1280 × 720. By entering these values into the tool, you will get a confirmed proportion match at 16:9 with a scale factor of 0.67× instantly.

Frequently Asked Questions

Enter the image width and height in pixels into the Ratio Finder tab. The calculator divides both values by their Greatest Common Divisor (GCD) to display the simplified ratio, such as 16:9 or 4:3.

Go to the Missing Dimension tab. Enter your known dimension (width or height), select which one it is, and enter the target ratio. The calculator multiplies or divides by the ratio to find the missing value.

When you fill in both Original and Target dimensions in the Ratio Finder tab, the tool checks whether they share the same aspect ratio. A green indicator means the proportions match; amber means they differ.

The scale factor shows how much larger or smaller the target dimensions are compared to the original. A scale factor of 0.5× means the target is half the size; 2.0× means it is twice as large.

YouTube recommends 16:9 for all uploads. The standard HD resolution is 1920×1080 pixels. The minimum recommended width is 1280 pixels at 16:9, which gives a height of 720 pixels.

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