#2 drill bit size
0.221 in
5.61 mm · number drill
| Inches | 0.221 in |
| Millimetres | 5.61 mm |
| Nearest metric drill | 5.6 mm |
| System | Number (#1 to #60) |
What #2 means
A bit marked #2 is a number drill, and the number is an index rather than a measurement — the higher the number, the smaller the bit. #1 is 0.228 inches and #60 is 0.04. That is the opposite of the fractional sizes stamped on a home set, which is why a number drill and a fraction of similar appearance can be very different holes.
The same hole in the other systems
Three drill systems overlap across this range and a workshop rarely has all three. The nearest bit of each other kind to #2:
| System | Nearest size | Difference |
|---|---|---|
| letter | A — 0.234 in | 0.013 in larger |
| fractional | 7/32" — 0.2188 in | 0.0023 in smaller |
| metric | 5.6 mm | 0.013 mm smaller |
One of those is within three thousandths of an inch, which is inside the tolerance of most hand-held work — substitute it and nobody will know.
What gets drilled at 0.221 inches
Where the quarter-inch and five-sixteenths taps are drilled, and where clearance holes for small bolts begin. The three drill systems overlap most densely across this band, which is why a bit here is the one most often picked up and misidentified.
Either side of it
| Drill | Inches | Millimetres |
|---|---|---|
| #4 | 0.209 in | 5.31 mm |
| #3 | 0.213 in | 5.41 mm |
| 7/32" | 0.2188 in | 5.56 mm |
| #2 | 0.221 in | 5.61 mm |
| #1 | 0.228 in | 5.79 mm |
| A | 0.234 in | 5.94 mm |
| 15/64" | 0.2344 in | 5.95 mm |
Frequently asked questions
What size is a #2 drill bit?
0.221 inches, which is 5.61 mm. Number drills run from #1 at 0.228 inches down to #60 at 0.04, getting smaller as the number rises — the opposite of what most people expect the first time.
What is a #2 drill bit in mm?
5.61 mm. A metric index will offer 5.6 mm as the nearest stocked size, which is near enough identical.
Is #2 a tapping drill size?
Not for any of the unified threads on this site. It sits between the sizes the standard taps call for, so it is a clearance or pilot drill rather than a tapping one.
What is the next size up from #2?
#1 at 0.228 inches — 0.007 inches larger. Below it is 7/32" at 0.2188.
Other sizes
- #1 drill bit — 0.228 in, 5.79 mm
- A drill bit — 0.234 in, 5.94 mm
- 15/64" drill bit — 0.2344 in, 5.95 mm
- B drill bit — 0.238 in, 6.05 mm
- C drill bit — 0.242 in, 6.15 mm
- D drill bit — 0.246 in, 6.25 mm
- E drill bit — 0.25 in, 6.35 mm
- 1/4" drill bit — 0.25 in, 6.35 mm