3/8" drill size
A 3/8 in drill is 0.3750 in (9.52 mm). It sits between 23/64 in and 25/64 in in the fractional series; the nearest metric drill is 9.5 mm.
3/8" at a glance
Decimal, metric and the nearest sizes in the other series.
Nearest metric drills
Metric drills step by 0.05 mm below 3 mm and by 0.1 mm from 3 mm. Difference is metric minus inch size.
| Metric drill | Inch | Difference | In inches | Hole |
|---|---|---|---|---|
| 9.5 mm | 0.3740" | −0.025 mm | −0.0010" | Smaller |
| 9.6 mm | 0.3780" | +0.075 mm | +0.0030" | Larger |
Nearby inch drills
The next size down and up in each inch series, so you can pick a substitute from the drawer.
Threads a 3/8" drill can tap
Threads from the tap tables on this site that this drill can tap, with the thread percentage it leaves (55–85 % shown).
| Thread | Standard drill | Thread with this drill | Suits |
|---|---|---|---|
| 7/16-14 UNC | U | 67 % | Good in steel |
Clearance for screws and bolts
Bolts and screws a 3/8" hole clears, with the diametral clearance and the gap each side. Metric sizes are compared with ISO 273.
| Fastener | Diameter | Clearance | Per side | ISO 273, metric only |
|---|---|---|---|---|
| 5/16" bolt | 0.3125" | 0.0625" | 0.0312" | – |
| M8 bolt | 8 mm | 1.52 mm | 0.76 mm | Normal fit (normal 9, loose 10 mm) |
Inch clearance is the drill size minus the basic major diameter. A drilled hole usually cuts slightly oversize.
Fractional drill index
Every size in the series, holes drawn to scale.
Common questions
What size is a 3/8 in drill?
A 3/8 in drill is 0.3750 in, which is 9.52 mm (9.5250 mm exactly).
What is the metric equivalent of a 3/8 in drill?
The nearest metric drill is 9.5 mm, 0.025 mm smaller. The other close size is 9.6 mm.
What thread can I tap with a 3/8 in drill?
It leaves about 67 % thread in 7/16-14 UNC.
Which number or letter drill is closest to 3/8 in?
Letter V (0.3770 in) is the closest, 0.0020 in larger.
What does a 3/8 in drill clear?
It clears a M8 bolt with 1.52 mm total clearance (0.76 mm per side); for metric bolts: normal fit.