Norm to convert imperial to metric you can bookmark a page on the internet on your phone or remember that 1" is 25.4mm
so
3/4 inch
25.4 divided by 4 (dividing one inch into quarters)
1/4 inch is 6.35mm
times 3 (to give 3 quarters of an inch)
19.05
Alternatively, some drill bit manufacturers have printed conversion charts available for the garage wall.
