Zippers are always measured from "component to component" (end stops), regardless of zipper style. The illustrations below will assist you in determining the proper method for arriving at the desired zipper length.

OPEN TOP, CLOSED BOTTOM	OPEN TOP, OPEN BOTTOM SEPARATING	CLOSED TOP, CLOSED BOTTOM
OPEN TOP, OPEN BOTTOM TU-WAY SEPARATING	CLOSED AT BOTH ENDS MULTIPLE SLIDERS	OPEN AT ONE END, CLOSED AT ONE END MULTIPLE SLIDERS