Free workshop tools
Calculators that answer the question in one screen
No sign-up, no ads, nothing to install. Built by the people who spec these tools, because we got tired of scrolling past four paragraphs to find one number.
Drill Size Converter
Metric ↔ inch ↔ number ↔ letter
Type any drill designation — 6.8 mm, 3/16", #11, letter F — and get the other three systems plus the bit to actually order.
Open the toolTap Drill Calculator
Metric · UNC · UNF · BSW · BSP · NPT
Pick a thread and set the thread engagement. Charts assume 75%; stainless usually wants 60%, and that difference is what snaps taps.
Open the toolPrefer the tables? They are all here too
Every calculator above has the full reference table underneath it, and the guides section carries the printable versions — drill sizes, wall plugs, pilot holes, hole saws, disc sizes, RPM by material and more.
Why we built these
We sell the bits behind every number on this page
Xiaoman Tools supplies drill bits, taps, discs and blades factory-direct to importers and hardware distributors. Tell us the sizes and volumes — we quote in 24 hours.