Metric thread basic dimensions (pitch diameter, minor diameter, tap drill)
From the nominal diameter and pitch: the fundamental triangle height, pitch diameter, minor diameter (basic internal minor diameter) and a guide tap drill size for cutting taps.
⌇Thread dimensions calculator
Pitch diameter d2—mm
Minor diameter d1 (basic D1 of the nut)—mm
Fundamental triangle height H—mm
Tap drill guide (d − P)—mm
H = 0.866025 × P d2 = d − 0.649519 × P d1 = d − 1.082532 × P Tap drill guide = d − P
Notes
- These are basic dimensions (theoretical, no tolerance). Real bolts and nuts fall inside the tolerance zone of their class (6g, 6H, etc.).
- “d − P” is the common rule of thumb for cutting taps. Recommended sizes vary slightly by tap maker and tolerance class. Forming (roll) taps need a larger hole and each maker uses its own formula.
All values are guides. Start from the tool maker’s recommended cutting data and adjust for your machine, workholding and coolant. Calculations run in your browser; nothing you enter is sent anywhere.