Styleguide - The Numbers Game

As much as possible, we prefer sticking to relative units in a predictable scale. Base values are typically stored in Config (which we’ll cover in Foundation) and derived from that point on. For purposes of efficiency and standardization, you’ll define number values less often than usual in MVCSS.


  • A pixel value for a base font size (stored in Config) is set on the root html element, thereby preparing both text sizing and the relative value of an em unit
  • Line heights are unitless, e.g. 1.5
  • Spacing (padding, margin, etc.) is a multiple of a stored base space value, set in ems
  • Font sizes (aside from the html element) are defined with percentage values, scaling the other relative properties on the element simultaneously

This setup should be a easier to grasp once we reach the Config, Tools, and Base segments of Foundation.

Note: pixel values will occasionally be required to meet design requirements, especially with things like offsets. Most often, these are considered magic numbers, and you should avoid using them as much as possible.