#7 drill bit size
0.201 in
5.11 mm · number drill · tapping drill for 1/4-20
| Inches | 0.201 in |
| Millimetres | 5.11 mm |
| Nearest metric drill | 5.1 mm |
| System | Number (#1 to #60) |
| Taps | 1/4-20 |
What #7 means
A bit marked #7 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 #7:
| System | Nearest size | Difference |
|---|---|---|
| letter | A — 0.234 in | 0.033 in larger |
| fractional | 13/64" — 0.2031 in | 0.0021 in larger |
| metric | 5.1 mm | 0.005 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 #7 is for
#7 is the standard tapping drill for 1/4-20 at 75% thread engagement. That is not a coincidence of the tables: the theoretical figure for 1/4-20 works out at 0.2013 inches, and #7 at 0.201 is the nearest drill that exists.
What gets drilled at 0.201 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 |
|---|---|---|
| #10 | 0.1935 in | 4.91 mm |
| #9 | 0.196 in | 4.98 mm |
| #8 | 0.199 in | 5.05 mm |
| #7 | 0.201 in | 5.11 mm |
| 13/64" | 0.2031 in | 5.16 mm |
| #6 | 0.204 in | 5.18 mm |
| #5 | 0.2055 in | 5.22 mm |
Frequently asked questions
What size is a #7 drill bit?
0.201 inches, which is 5.11 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 #7 drill bit in mm?
5.11 mm. A metric index will offer 5.1 mm as the nearest stocked size, which is near enough identical.
What tap does a #7 drill bit go with?
1/4-20 at the standard 75% thread. That thread comes out at a theoretical diameter this drill is the nearest stocked size to.
What is the next size up from #7?
13/64" at 0.2031 inches — 0.0021 inches larger. Below it is #8 at 0.199.
Other sizes
- 13/64" drill bit — 0.2031 in, 5.16 mm
- #6 drill bit — 0.204 in, 5.18 mm
- #5 drill bit — 0.2055 in, 5.22 mm
- #4 drill bit — 0.209 in, 5.31 mm
- #3 drill bit — 0.213 in, 5.41 mm
- 7/32" drill bit — 0.2188 in, 5.56 mm
- #2 drill bit — 0.221 in, 5.61 mm
- #1 drill bit — 0.228 in, 5.79 mm