Lombard Insurance

The minimum amount of horizontal whitespace, i. e. primarily the separation between columns of body text (gutter), is governed by Gestalt psychology with font size, line spacing, and line width as main influencing factors. You should place text blocks far enough from another such that your recipients will be able to see them as distinct units of their own. A traditional rule of thumb would make the gutter at least 1.5 ems wide in order to appear significantly wider than any possible whitespace within a line of text. On the screen, good line spacing tends to be a little bit wider than in traditional print, though. Hence you will probably need a little bit more than that. Using the same value as your baseline grid is a good guess to start with in most cases.