METRIC DESIGN GUIDE
Conduit will not now change size in metric. It will be classified by a nominal mm
size. During transition to metric the following should be placed on at least the first
electrical sheet. These are NEMA standards.
"ALL CONDUIT SIZES ARE INDUSTRY STANDARD ENGLISH SIZE CONDUIT
DESIGNATED BY THEIR ROUNDED NOMINAL MILLIMETER (mm)
DIAMETER EQUIVALENT. SEE CHART BELOW."
Use AWG or MCM until availability of wire manufactured to ASTM B682, standard
metric conductor sizes, is determined. Round metric sizes per the above standard are
substantially larger than round English sizes in secondary circuit use. Fiber optic cables
are already metric.