Aspect Ratio Calculator

Calculate and resize image/video dimensions

About Aspect Ratio Calculator

Aspect ratio describes the proportional relationship between an image or video's width and height, expressed as two numbers (like 16:9 or 4:3). This calculator finds a missing dimension that preserves the original ratio, or simplifies a ratio to its smallest whole-number form.

Formula

New Height = New Width × (Original Height / Original Width) — or simplify Width:Height using their greatest common divisor (GCD)

How It Works

Enter your original width and height (or an aspect ratio like 16:9)
Enter a new width or height you want to resize to
The calculator finds the matching dimension that keeps the same width-to-height ratio
You can also enter two dimensions to find and simplify their aspect ratio

Tips

Common video ratios are 16:9 (widescreen), 4:3 (older TV/monitors), and 9:16 (vertical/mobile video)
Common photo ratios include 3:2 (standard DSLR), 4:3 (compact cameras), and 1:1 (square)
Resizing without preserving aspect ratio causes stretching or squishing — always scale both dimensions by the same factor

Frequently Asked Questions

How do I find the height for a new width while keeping the same ratio?

Multiply the new width by (original height ÷ original width). For example, resizing a 1920×1080 image to a width of 1280: 1280 × (1080/1920) = 720, giving 1280×720.

How do I simplify a ratio like 1920:1080?

Divide both numbers by their greatest common divisor. 1920 and 1080 share a GCD of 120, so 1920÷120 : 1080÷120 = 16:9.

What is the difference between 16:9 and 4:3?

16:9 is a wider, more rectangular ratio common in modern video and widescreen displays; 4:3 is more square-shaped and was standard for older televisions and monitors.

Why does my image look stretched after resizing?

The width and height were likely scaled by different factors, distorting the original proportions — use an aspect-ratio-preserving resize (scale both dimensions by the same factor) to avoid this.

What aspect ratio should I use for Instagram or TikTok?

Instagram supports 1:1 (square), 4:5 (portrait feed), and 9:16 (Stories/Reels); TikTok primarily uses 9:16 for vertical video — check the specific platform's current recommended ratio before exporting.