1/4 inch in mm and decimal

1/4 in = 0.25 in = 6.350 mm. Closest metric drill: 6.3 mm.

Nearby drill sizes

Drill	Type	Inch	mm	Difference
15/64	fraction	.2344 in	5.953	-15.6 thou
B	letter	.2380 in	6.045	-12.0 thou
C	letter	.2420 in	6.147	-8.0 thou
D	letter	.2460 in	6.248	-4.0 thou
E	letter	.2500 in	6.350	0.0 thou
1/4	fraction	.2500 in	6.350	0.0 thou
F	letter	.2570 in	6.528	7.0 thou
G	letter	.2610 in	6.629	11.0 thou
17/64	fraction	.2656 in	6.747	15.6 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.