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Aspect Ratio and Image Size Calculator

Enter two of width, height and aspect ratio, and the calculator works out the third. It also shows the simplest ratio of the size, so a 1920 by 1080 image is 16:9.

Width (pixels) Height (pixels) Aspect ratio (width:height)

Fill in two fields and leave the third empty. Whole numbers or decimals, for example 1280, 16.5 or 1.85:1.

Enter two of width, height and ratio.

Width-

Height-

Simplest ratio-

Rounding: a width or height worked out from the other values is rounded half up to a whole pixel (56.25 becomes 56, and 56.5 becomes 57). The exact value is shown when rounding happens. Sizes you type in are never changed.

How it works

The ratio is width divided by height, so width = height × ratio and height = width ÷ ratio. The calculator uses exact arithmetic, so the result is not affected by rounding errors in the browser. The simplest ratio divides the width and height by their greatest common divisor, so 1920 by 1080 becomes 16:9.

Nothing you type is sent anywhere or saved. The calculator runs entirely in your browser.