#40 Drill Size

number drill

#40 0.098 in 2.49 mm

A #40 drill measures 0.098 in. It taps 3 threads in this chart.

What a #40 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 #40 drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
#5-40	83.1%	#38	72.4%
M3 x 0.5	78.7%	2.5 mm	77.0%
#4-48	51.7%	#42	68.4%

Drills either side

2.45 mm 0.0965 in · 2.45 mm Next size down
2.5 mm 0.0984 in · 2.5 mm Next size up

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

#40 drill: common questions

What size is a #40 drill?

0.098 inches, which is 2.49 mm. It is a number drill.

What can I tap with a #40 drill?

3 threads: #5-40 at 83.1%, M3 x 0.5 at 78.7%, #4-48 at 51.7%.

What drill is next to a #40?

Down: 2.45 mm at 0.0965 in. Up: 2.5 mm at 0.0984 in.