What is an aspect ratio?

The proportional relationship between width and height. 16:9 means for every 16 units wide, it's 9 units tall.

What are common aspect ratios?

16:9 (widescreen), 4:3 (standard), 1:1 (square), 21:9 (ultrawide), 9:16 (vertical/mobile).

How do I maintain aspect ratio when resizing?

Enter your original dimensions to find the ratio, then enter a new width or height — the other dimension is calculated automatically.

Aspect Ratio Calculator

Calculate aspect ratios from dimensions. Find the matching width or height for any ratio.

Presets

Width

Height

Enter width and height to find the aspect ratio.

Frequently asked questions

Aspect Ratio Calculator — Free Online

Calculate aspect ratios from pixel dimensions, or find the missing dimension given a ratio and one side. Essential for video editing, image resizing, and responsive design.

Auto-detect ratio

Enter width and height to find the simplified ratio.

Calculate missing side

Enter ratio + one dimension to find the other.

Common presets

Quick buttons for 16:9, 4:3, 1:1, 21:9, 9:16.