Pragmatic Guide to Sass 3

9	Calculating a Simple Layout

Sass allows you to do calculations on the fly and in your document: you can easily type width: 12px * 0.5; in your code!

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OK, OK—we admit that’s not terribly useful. But it is once you throw variables into the mix. Once you’ve defined a variable, Sass allows you to perform basic operations on that variable using standard operators for adding, subtracting, multiplying, and dividing (+, -, *, and /). The operators will be familiar to anyone who has done any amount of programming before.

You could say something like width: $page_width * 0.1 as a way to avoid hard-coding pixel values. When the CSS is compiled, this will be precalculated and will print out an exact width in pixels.

You can now do the previously laborious ...