IMAGE TOOL

Aspect Ratio Calculator

Calculate aspect ratio, find missing width or height, and scale images perfectly. Presets for 16:9, 4:3, 1:1 and more — with live visual preview.

✓ Free to use ✓ GCD simplified ratio ✓ Lock & scale ✓ Image auto-detect
// ASPECT_RATIO_CALCULATOR

Calculate Ratio

LOCAL
⬢

Drop image to auto-detect dimensions

JPG, PNG, WebP, GIF — processed locally

Dimensions

px
px
:
16 : 9
1.78 : 1 decimal 1920 × 1080 • GCD 120
Changing width auto-updates height

Common Presets

Visual Preview & Scale

16 : 9

Common Resolutions (click to apply)

How to use the aspect ratio calculator

  1. Enter width and height — or drop an image to auto-fill. The simplified ratio appears instantly.
  2. Lock the ratio — keep it enabled to auto-calculate the missing side when you change one dimension.
  3. Use presets — click 16:9, 4:3, 1:1, etc. to apply instantly, or pick a common resolution like 1920×1080.
  4. Scale — enter a new width or height to see the proportional scaled size and preview.

What is aspect ratio?

Aspect ratio is the proportional relationship between width and height, written as width:height. For example, 1920×1080 simplifies to 16:9 by dividing both by their GCD (120). It tells you the shape — widescreen, square, or portrait — regardless of actual pixels.

16:9Widescreen • Video
4:3Classic • Photo
1:1Square • Instagram
9:16Vertical • Reels

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Frequently Asked Questions

How do I calculate aspect ratio?

Enter width and height. We compute the greatest common divisor (GCD) and divide both numbers — e.g., 1920÷120=16 and 1080÷120=9, so 16:9. You also get decimal (1.78:1) and percentage.

How to find the missing width or height?

Keep “Lock aspect ratio” enabled. Enter your ratio (e.g., 16:9) and the known side. The missing side is calculated as height = width × ratioH / ratioW (or vice versa) instantly.

What are the most common aspect ratios?

16:9 for YouTube and widescreen, 4:3 for classic TV, 1:1 for Instagram posts, 3:2 for DSLR photos, 21:9 for ultrawide monitors, and 9:16 for TikTok/Reels vertical video.

Can I detect ratio from an image?

Yes — drag & drop any JPG, PNG, WebP, or GIF. The tool reads its naturalWidth/naturalHeight locally and fills the calculator. No upload, 100% private.

Does this work offline?

Yes, all math runs in your browser with vanilla JavaScript. No server, no tracking. You can even save the page and use it offline.