Tap Drill Size Chart

#1 Drill Size

number drill

#1 0.228 in 5.79 mm

A #1 drill measures 0.228 in. It taps 1 thread in this chart.

What a #1 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 #1 drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread % thread Chart drill Chart %
1/4-32 54.2% 7/32″ 76.9%

Other jobs for a #1

Hard-material tap drill
The size to use in stainless or tool steel for 1/4-32, where it leaves a shallower thread than the standard drill and cuts tapping torque.
Form-tap hole
The published roll-tap hole for 1/4-20. A form tap displaces metal instead of cutting it, so it needs this larger hole.

Drills either side

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

#1 drill: common questions

What size is a #1 drill?
0.228 inches, which is 5.79 mm. It is a number drill.
What can I tap with a #1 drill?
1 thread: 1/4-32 at 54.2%.
What drill is next to a #1?
Down: 5.7 mm at 0.2244 in. Up: A at 0.234 in.