All countries in the world except USA, Liberia, and Myanmar use millimeters (mm).   USA citizens:  Conversion factor is 25.400000 mm/inch.  Areas herein are accurate to five significant digits using exact converted USA diameters and pitches (not rounded USA diameters and pitches listed herein).  M and MJ are metric thread profiles.  Size designations not beginning with "M" in Table 1 are UN and UNJ thread profiles (non-metric).  Blank values in Table 1 mean nonexistent fastener size.  Dark shaded values mean typically never used and typically unavailable fastener size.

M and MJ are metric thread profiles.  Size designations not beginning with "M" in Table 1 are UN and UNJ thread profiles (non-metric), no longer used anywhere in the world except in a few behind-the-times organizations in USA.

You can look up each value in Table 1, above, or you can use the Table 2 formulas to calculate the values yourself.  In the following table, D_n is nominal shank diameter (fastener size) from Table 1.  Pitch p is fastener longitudinal length per thread.  Note that p = 1 / n, where n = threads per unit length.  L_e is thread engagement length.
 

Thread engagement length.  In general, according to Machine Design magazine, the minimum recommended length of engagement is 0.75 to 1 times the bolt major diameter for threading into steel and other materials of comparable hardness; and 1 to 1.5 times the bolt major diameter for threading into brass, cast iron, and aluminum.  These lengths of engagement specified are for full threads engaged, not overall bolt length.  Regarding partial threads in the chamfers on the ends of internal or external threads, FED-STD-H28/2B, 1991, Sect. 7.7.2, p. 61, specifies that approximately half the countersink or chamfer depth may be included in the length of engagement calculation.