UX Design and Development course

CSS Calc


CSS is a complete conundrum; we all appreciate CSS because of its simplicity but always yearn for the language to do just a bit more. CSS has evolved to accommodate placeholders, animations, and even click events. One problem we always thought we'd have with CSS, however, was its static nature; i.e. there's really no logic, per se. The CSS calc routine bucks that trend, providing developers an ounce of programming ability within CSS.


The calc routine is especially useful when calculating relative widths. Calculations can be additions, subtractions, multiplications, and divisions. Have a look:

/* basic calc */
.simpleBlock {
  width: calc(100% - 100px);

/* calc in calc */
.complexBlock {
  width: calc(100% - 50% / 3);
  padding: 5px calc(3% - 2px);
  margin-left: calc(10% + 10px);

WebKit and Opera currently require a browser prefix for calc(). Be sure to use whitespace around operators so that they aren't construed as positive and negative notations.

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CSS calc is another example of CSS taking over the role of JavaScript in layout, and I think it's a great thing. As we move more toward responsive design, calc allows us to use percentages for overall block widths, with just a touch of pixel help for some of its components. Have you used calc for your apps? Share how you used calc!