#3 drill size
A #3 drill is 0.2130 in (5.41 mm). It is the standard tap drill for 1/4-28 UNF; the nearest metric drill is 5.4 mm.
#3 at a glance
Decimal, metric and the nearest sizes in the other series.
- Decimal inch
- 0.2130"
- Millimetres
- 5.41 mm 5.4102
- Nearest metric drill
- 5.4 mm −0.010 mm
- Nearest fractional
- 7/32" 0.2188", +0.0058"
- Hole area
- 0.0356 in² 22.99 mm²
- Tap drill for
- 1/4-28 UNF
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 |
|---|---|---|---|---|
| 5.4 mm | 0.2126" | −0.010 mm | −0.0004" | Smaller |
| 5.5 mm | 0.2165" | +0.090 mm | +0.0035" | 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 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 |
|---|---|---|---|
| 1/4-28 UNF | #3 | 80 % | Standard drill |
| M6 × 0.75 | 5.2 mm | 61 % | Hard, tough metals |
| 1/4-20 UNC | #7 | 57 % | Hard, tough metals |
Clearance for screws and bolts
Bolts and screws a #3 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 |
|---|---|---|---|---|
| #8 screw | 0.1640" | 0.0490" | 0.0245" | – |
| #10 screw | 0.1900" | 0.0230" | 0.0115" | – |
| M5 bolt | 5 mm | 0.41 mm | 0.21 mm | Close fit (close 5.3, normal 5.5 mm) |
Inch clearance is the drill size minus the basic major diameter. A drilled hole usually cuts slightly oversize.
Number drill index
Every size in the series, holes drawn to scale.
Common questions
What size is a #3 drill?
A #3 drill is 0.2130 in, which is 5.41 mm (5.4102 mm exactly).
What is the metric equivalent of a #3 drill?
The nearest metric drill is 5.4 mm, 0.010 mm smaller. The other close size is 5.5 mm.
What tap uses a #3 drill?
A #3 drill is the standard tap drill for 1/4-28 UNF (about 80 % thread).
Which fractional drill is closest to #3?
7/32 in (0.2188 in) is the closest, 0.0058 in larger.
What does a #3 drill clear?
It clears a M5 bolt with 0.41 mm total clearance (0.21 mm per side); for metric bolts: close fit.