#8 Drill Size

number drill

#8 0.199 in 5.06 mm

A #8 drill measures 0.199 in. It taps 2 threads in this chart.

What a #8 drill taps

Every thread this drill cuts between 50% and 85% of thread, deepest first. Outside that band it is the wrong drill for the job, so nothing below that line is listed.

Threads a #8 drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
1/4-20	78.5%	#7	75.4%
M6 x 1	72.7%	5 mm	77.0%

Other jobs for a #8

Form-tap hole: The published roll-tap hole for #12-24. A form tap displaces metal instead of cutting it, so it needs this larger hole.

Drills either side

5 mm 0.1969 in · 5 mm Next size down
5.1 mm 0.2008 in · 5.1 mm Next size up

All drill sizes → · Open this drill in the calculator →

#8 drill: common questions

What size is a #8 drill?

0.199 inches, which is 5.06 mm. It is a number drill.

What can I tap with a #8 drill?

2 threads: 1/4-20 at 78.5%, M6 x 1 at 72.7%.

What drill is next to a #8?

Down: 5 mm at 0.1969 in. Up: 5.1 mm at 0.2008 in.