Aspect Ratio Calculator - Free Online Image & Video Scaling Tool

How to Use the Proportional Resizer

Enter the width and height of your source media in the input fields.
The tool calculates the simplified ratio (e.g. 16:9, 4:3) and the GCD.
Enter a new width (or height) in the scale section to get the proportional dimension.
Use the presets panel to jump to common ratios: 16:9, 4:3, 1:1, 21:9.

Aspect Ratio Calculator: find simplified ratios and scale dimensions proportionally. Maintaining the correct pixel aspect ratio when scaling images or video prevents distortion - a 1920×1080 frame scaled to 1280 width must be 720 pixels tall, not 900. This simplified ratio finder works for any resolution, ensuring your image scaling tool needs are met with mathematical precision.

Common Screen Ratio Tool Presets

16:9 is the standard widescreen ratio for HD and 4K video, YouTube, and most monitors. 4:3 was the original television standard, while 1:1 is used for Instagram square posts. Modern 21:9 (ultrawide) and 9:16 (portrait) ratios are also supported. This 16:9 calculator handles any arbitrary resolution, giving you the exact decimal ratio and simplified fraction for professional video resolution scaling and design workflows.

Simplifies any width×height to its lowest-terms ratio using GCD
Calculates missing dimension from a known target width or height
Presets for 16:9, 4:3, 1:1, 3:2, 2:1, 9:16, 21:9
Shows exact decimal ratio for precise comparison

Frequently Asked Questions

What does "simplified" ratio mean?

3840×2160 simplifies to 16:9 by dividing both values by their greatest common divisor (480). Simplified ratios make comparisons easier - any 16:9 resolution simplifies to 16:9.

Why is 1920×1080 called "16:9" when 1920÷16=120 and 1080÷9=120?

Both 1920 and 1080 are divisible by 120. Dividing both by 120 gives 16:9. The GCD of 1920 and 1080 is 120.

How do I find the height for a 1280-wide 16:9 image?

Divide 1280 by 16 to get one unit (80), then multiply by 9: 80 × 9 = 720. Or use the scale section of this calculator - enter the known dimension and it computes the other.

What ratio does a 4K cinema frame use?

DCI 4K is 4096×2160, which simplifies to 256:135 - slightly wider than 16:9. Consumer 4K (UHD) is 3840×2160 = 16:9.

For more advanced dimension management, bookmark this fast and accurate Aspect Ratio Calculator.

Aspect Ratio Calculator online

Instantly find the simplified ratio and scale resolution dimensions.