Tap Drill Size Calculator
Tap Drill Size
Calculate the tap drill diameter for threaded holes.
Formula
Drill = Major Dia - Thread% x 1.299 x Pitch
Frequently Asked Questions
What thread percentage should I use?
Use 75 percent for most applications. Going above 80 percent adds little strength.
How do I find threads per inch?
Use a thread pitch gauge or count threads over one inch of the fastener.