FREE · CALCULATORS & CONVERTERS
Tap Drill Calculator.
Estimate a tap drill from the major diameter, pitch and a thread percentage.
Drill = major − pitch × (percent / 75). At 75% this matches the common one-pitch chart rule. It is a shop estimate, not a gauge inspection. Local arithmetic only. This is a quantity or geometry estimate, not a code check and not a substitute for a licensed professional.
- Tap drill
- 8.5 mm
Drill diameter = major diameter − pitch × (thread percent / 75). At 75% this is the common chart rule of one pitch under the major diameter. It is a shop estimate, not a thread-gauge inspection.
How to use Tap Drill Calculator
Pick a common metric size or enter a major diameter and pitch. 75% uses one pitch under the major diameter.
How it works
Estimate a tap drill from the major diameter, pitch and a thread percentage. Drill = major − pitch × (percent / 75). At 75% this matches the common one-pitch chart rule. It is a shop estimate, not a gauge inspection. Local arithmetic only. This is a quantity or geometry estimate, not a code check and not a substitute for a licensed professional.
Example
M10 × 1.5 at 75% thread → 8.5 mm.
Questions about Tap Drill Calculator
Is Tap Drill Calculator free, and do I need an account?
Yes. This tool is free to use in your browser without an account. Processing takes place on your device.
What are the limits and what should I check?
Drill = major − pitch × (percent / 75). At 75% this matches the common one-pitch chart rule. It is a shop estimate, not a gauge inspection. Local arithmetic only. This is a quantity or geometry estimate, not a code check and not a substitute for a licensed professional. Review the result before using it in your work.
Is my input sent to a server?
Your input is processed in your browser and is not uploaded by this tool. Files and pasted text are cleared when the page is refreshed. Normal website requests are still required to load the page and its libraries. Read the privacy explanation.