Some of them work out to really crap metric equivalents.

If it is not critical measurements you can round to the nearest mm or 0.1mm I guess?

TELECASTER ROUTES:
NECK POCKET: 0.625” = 15.875mm
NECK PICKUP: 0.687” = 17.449mm
WIRING ROUTE: 0.687”
BRIDGE PICKUP: 0.850” = 21.59mm
CONTROL CAVITY: 1.50” (1.25” ON THINNER BODIES) 38.1mm/ 31.7mm
BODY THICKNESS: 1.75” (50’s TELE’s varied from 1.50” to 1.75”) =44.45mm
ROUNDOVERS: 1/8” =3.175mm

It depends how many decimal places you want to go to.