Headspace in a rimmed cartridge is measured from the bottom of the rim recess to the face of the breech, and is therefore only slightly greater than the thickness of the rim on the cartridge. With a belted case, headspace is measured from the bottom of the belt recess in the chamber to the breech face.

In both cases, measurement is made using simple "button" style gauges for "go" and "no go" purposes. (The "go gauge" represents the correct spacing and allows a properly headspaced weapon to close on it, the "no go guage" should prevent the action from closing. If the action closes on a "no go guage", then headspace is excessive.)