A CodePen by leison. Nestable Fluid Grid Math - This is your typical fluid grid that allows you to nest a another fluid grid while having it look right and having the inner spans add up like you'd expect.

The problem with nesting a fluid grid is its percentage based widths and gutters. They calculate from the parent column's width, not the container you specified.

This nested fluid grid appears as you would expect it to by adjusting the inner gutter and column width. Additionally, there is no need for omega or nth-child selections because it uses the gutter-as-a-negative-margin on the parent row. (also adjusted as a percent).