Need to find the right drill bit size for a hole? Drill Calc calculates the correct drill bit size to use for threaded holes, based on the bolt (tap) diameter and thread pitch and percentage, for both inch and metric threads. Close and tight fit hole sizes for many popular drill sizes are also displayed.

It also has tables of standard inch fractional and numeric drill bit sizes, as well as complete information for various pipe sizes. There is also detailed information about the commonly used sizes of wood screws.

Buy your copy of Drill Calc today, and put away your drill chart.

What’s New

Version 2.4

This app has been updated by Apple to use the latest Apple signing certificate.

Added information for wood screws.
Combined list of numeric and fractional drill sizes.
Updates for iOS 9.3.

Ratings and Reviews

4.7 out of 5
9 Ratings

9 Ratings

Gilberto Diaz ,


This app puts at my fingers all the data I could ever need in the machine shop when tapping time comes around. Very detailed and accurate.

Billw37 ,

Good, but could be better

I am a hobbyist machinist. I am always using Drill Calc for looking up drill sizes when I am threading. One feature I would appreciate is an all encompassing decimal lookup chart. This single chart would contain fractional, lettered, numbered and metric drill sizes.
I also would find it helpful if you supplied the data for doing external threading.

Dieguy ,

Works well

Functionality of app is great! Good clean layout. I agree that pipe theads would be a great addition, as well as fine threads for metric taps. Clearance drills, counterbores, and reamer drill sizes would also be a welcomed upgrade. I would pay extra for those options even. Keep up the good work

App Privacy

The developer, Black Cat Systems, has not provided details about its privacy practices and handling of data to Apple.

No Details Provided

The developer will be required to provide privacy details when they submit their next app update.


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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