Tap drill size calculator

1Type your thread

Or tap an example:

2What are you drilling?

Soft metalAluminum, brass, plasticSteelMild and carbon steelStainlessStainless, titanium

Harder metals get a bigger drill, so the tap works less hard.

3Your drill

For 1/4-20 in aluminum, brass, plastics, use #7 (0.2010 in, 5.11 mm). It leaves about 75% thread, right on the 75% target.

No #7? The closest metric drill is 5.1 mm (0.2008 in), about 76% thread.

Already have a drill? Check itPick the drill you own to see how much thread it leaves.

Thread not in the list? Enter its size

Custom thread size Units Major diameter, inches Threads per inch

TapDrillSize: full tap drill charts and thread pages