Skip to content
QR Code Tools logo
QR Code Tools
Sign in
Image Resizerby Free QR Code Tools

Aspect Ratio Calculator

Enter any width and height and get the simplified aspect ratio (1920×1080 becomes 16:9), the decimal form, and a proportional resize calculator: give a new width and the matching height is worked out for you. Handy before cropping, embedding video, or briefing a designer.

Aspect ratio
16:9
Decimal
1.7778

New size: 800 × 450px

The maths: DPI = pixels ÷ inches. A pixel count alone is never 300 DPI — DPI only exists once a physical print size is chosen. Screens, by contrast, just use pixels.

How to aspect Ratio Calculator

  1. Enter width and height.
  2. Read the simplified ratio.
  3. Optionally type a new width to get the matching height.

Frequently asked questions

What are the common ratios?

16:9 (video, YouTube), 4:5 (Instagram portrait), 1:1 (square posts), 3:2 (classic photo), 4:3 (older screens, iPad), 21:9 (ultrawide), 9:16 (Stories, Reels, TikTok).

Why does my ratio show huge numbers?

Some dimensions share no common divisor (e.g. 1000×563 is already simplest). The decimal form is then the practical one to use.

Related tools

DPI CalculatorEffective DPI at any print size — and the pixels needed to hit 300 DPI.Print Size CalculatorFrom pixels + DPI to real-world size: inches, centimetres and millimetres.Crop ImageCut out exactly the part of the picture you need — by dragging, or by the pixel.Image ResizerChange any image to exact pixel dimensions, by width, height or percentage.