1/8" drill size
A 1/8 in drill is 0.1250 in (3.17 mm). It sits between 7/64 in and 9/64 in in the fractional series; the nearest metric drill is 3.2 mm.
1/8" 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 |
|---|---|---|---|---|
| 3.1 mm | 0.1220" | −0.075 mm | −0.0030" | Smaller |
| 3.2 mm | 0.1260" | +0.025 mm | +0.0010" | 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 1/8" drill can tap
No thread in the tap tables on this site falls between 55 and 85 % thread with this drill, so it is not a useful tap drill for them. Drills this size are mostly used for clearance, pilot and pin holes.
Clearance for screws and bolts
Bolts and screws a 1/8" 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 |
|---|---|---|---|---|
| #1 screw | 0.0730" | 0.0520" | 0.0260" | – |
| #2 screw | 0.0860" | 0.0390" | 0.0195" | – |
| #3 screw | 0.0990" | 0.0260" | 0.0130" | – |
| #4 screw | 0.1120" | 0.0130" | 0.0065" | – |
| M3 bolt | 3 mm | 0.17 mm | 0.09 mm | Tighter than close fit (3.2 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 1/8 in drill?
A 1/8 in drill is 0.1250 in, which is 3.17 mm (3.1750 mm exactly).
What is the metric equivalent of a 1/8 in drill?
The nearest metric drill is 3.2 mm, 0.025 mm larger. The other close size is 3.1 mm.
Which number or letter drill is closest to 1/8 in?
#30 (0.1285 in) is the closest, 0.0035 in larger.
What does a 1/8 in drill clear?
It clears a M3 bolt with 0.17 mm total clearance (0.09 mm per side); for metric bolts: tighter than close fit.