The good Mitutoyo digital caliper I use is either .0000" or .00 mm. so I have to look at measuring as a draw.
An inch is 2.54 cm or 25.4 mm, thus an inch is more than 25 times
larger than a milimeter. The fact that your caliper goes to 4 decimal
places in inches doesn’t necessarily mean more precison than when
dealing in milimeters. You are just subdividing a much larger unit of
measure. A measure of 0.0001 inch is the same as 0.00254 mm.
Robert Lowe, Lowe Assoicates - Brasil
Gemstones, Rough, Specimens