# #16 drill size

A #16 drill is 0.1770 in (4.50 mm). It is the standard tap drill for #12-24 UNC; the nearest metric drill is 4.5 mm.

## #16 drill data

- Series: Number drill
- Decimal: 0.1770 in
- Metric: 4.50 mm (4.4958 mm exact)
- Nearest metric drill: 4.5 mm (+0.004 mm)
- Nearest fractional: 11/64" (0.1719 in)
- Standard tap drill for: #12-24 UNC

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 4.4 mm | 0.1732 | −0.096 mm |
| 4.5 mm | 0.1772 | +0.004 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| 11/64" | Fractional | 0.1719 | 4.37 |
| #17 | Number | 0.1730 | 4.39 |
| #16 | Number | 0.1770 | 4.50 |
| #15 | Number | 0.1800 | 4.57 |
| 3/16" | Fractional | 0.1875 | 4.76 |
| Letter A | Letter | 0.2340 | 5.94 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| #12-24 UNC | #16 | 72 |
| M5 × 0.5 | 4.5 mm | 78 |
| #12-28 UNF | #14 | 84 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| #5 screw | 0.1250" | 0.0520" | 0.0260" | – |
| #6 screw | 0.1380" | 0.0390" | 0.0195" | – |
| M4 bolt | 4 mm | 0.50 mm | 0.25 mm | Close fit (close 4.3, normal 4.5 mm) |
| #8 screw | 0.1640" | 0.0130" | 0.0065" | – |


## FAQ

**What size is a #16 drill?**
A #16 drill is 0.1770 in, which is 4.50 mm (4.4958 mm exactly).

**What is the metric equivalent of a #16 drill?**
The nearest metric drill is 4.5 mm, 0.004 mm larger. The other close size is 4.4 mm.

**What tap uses a #16 drill?**
A #16 drill is the standard tap drill for #12-24 UNC (about 72 % thread).

**Which fractional drill is closest to #16?**
11/64 in (0.1719 in) is the closest, 0.0051 in smaller.

**What does a #16 drill clear?**
It clears a #8 screw with 0.0130" total clearance (0.0065" per side).

Source page: https://machinistcharts.com/drill-size/number-16/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)