Tools
Tap Drill Size Calculator
The tap drill size provides approximately 75% thread engagement, which is the industry standard for optimal strength and tap life.
Tap Drill Size Calculator
Select thread → Get drill size
Thread Size
The tap drill size provides approximately 75% thread engagement, which is the industry standard for optimal strength and tap life.
Thread Pitch
1.25mm
Clearance Hole
8.4mm
Selected ThreadM8
75% thread engagement • ISO 965-1 tolerance class 6H
Data for steel and stainless steel
How to Use the Tap Drill Size Chart
The Formula
The standard formula for calculating tap drill size is:
Tap Drill = Major Diameter - Pitch
- Major Diameter: The nominal thread size (e.g., 8mm for M8).
- Pitch: The distance between thread crests in mm (e.g., 1.25mm for M8 coarse).
- Result: M8 × 1.25 → Tap Drill = 8 - 1.25 = 6.75mm (rounded to 6.8mm)