25/64 inch in mm and decimal

25/64 in = 0.390625 in = 9.922 mm. Closest metric drill: 9.9 mm.

Taps that use a 25/64 drill

Drill	Type	Inch	mm	Difference
U	letter	.3680 in	9.347	-22.6 thou
3/8	fraction	.3750 in	9.525	-15.6 thou
V	letter	.3770 in	9.576	-13.6 thou
W	letter	.3860 in	9.804	-4.6 thou
25/64	fraction	.3906 in	9.922	0.0 thou
X	letter	.3970 in	10.084	6.4 thou
Y	letter	.4040 in	10.262	13.4 thou
13/32	fraction	.4063 in	10.319	15.6 thou
Z	letter	.4130 in	10.490	22.4 thou

1 thou = 0.001 in = 0.0254 mm. Drills a few thou apart are usually interchangeable for clearance holes, but not for tap drills or reamer pilots.