A gutter size calculator”What’s the best margins/gutter size to use for my book?” This is a common question I often see. While margins are more of an author’s general preference, the gutter case could use a calculator. The gutter calculator only works for perfect bound books of any type or size. Here’s the formulas, in C-programming style (there are two separate formulas, one for black and white (since it uses thinner paper) and another for color (since it uses thicker paper)):