1 in Drill Size

fractional drill

1″ 1.000 in 25.40 mm

A 1 in drill measures 1.000 in. It taps 3 threads in this chart.

What a 1 in 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 in drill taps, with the percent of thread each one gets and the published chart drill for comparison.
Thread	% thread	Chart drill	Chart %
M27 x 1.5	82.1%	25.5 mm	77.0%
1-1/8-7	67.4%	63/64″	75.8%
M27 x 2	61.6%	25 mm	77.0%

Drills either side

63/64″ 0.9844 in · 25 mm Next size down
25.5 mm 1.0039 in · 25.5 mm Next size up

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

1 in drill: common questions

What size is a 1 in drill?

1.000 inches, which is 25.40 mm. It is a fractional drill.

What can I tap with a 1 in drill?

3 threads: M27 x 1.5 at 82.1%, 1-1/8-7 at 67.4%, M27 x 2 at 61.6%.

What drill is next to a 1 in?

Down: 63/64 in at 0.9844 in. Up: 25.5 mm at 1.0039 in.