How far apart should I space dog holes on a workbench?

I'm building my first real woodworking workbench complete with a bench vise. But I'm wondering how far apart to space the dog holes. Is there a standard?
—Kenneth Grado, Lombard, Ill.

Ideally, space the dog holes so you can secure a board of any width to the workbench, Ken, so start by measuring your vise's capacity. For example, if the vise's jaws can hold a board up to 6¹⁄₂ ", secure any board up to that size between the jaws. But a board larger than that must be secured between the vise dog and a bench dog. So, with the vise jaws closed, locate the first hole 6" from the vise's dog—a little less than the vise's capacity. A dog in this hole can now hold a board from 6" to 12¹⁄₂  ", overlapping the vise capacity just a little. Then bore dog holes in 6" increments from the center of the first hole until you run out of benchtop.