# #66 drill size

A #66 drill is 0.0330 in (0.84 mm). It sits between #67 and #65 in the number series; the nearest metric drill is 0.85 mm.

## #66 drill data

- Series: Number drill
- Decimal: 0.0330 in
- Metric: 0.84 mm (0.8382 mm exact)
- Nearest metric drill: 0.85 mm (+0.012 mm)
- Nearest fractional: 1/32" (0.0312 in)

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 0.8 mm | 0.0315 | −0.038 mm |
| 0.85 mm | 0.0335 | +0.012 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| 1/32" | Fractional | 0.0312 | 0.79 |
| #67 | Number | 0.0320 | 0.81 |
| #66 | Number | 0.0330 | 0.84 |
| #65 | Number | 0.0350 | 0.89 |
| 3/64" | Fractional | 0.0469 | 1.19 |
| Letter A | Letter | 0.2340 | 5.94 |


## FAQ

**What size is a #66 drill?**
A #66 drill is 0.0330 in, which is 0.84 mm (0.8382 mm exactly).

**What is the metric equivalent of a #66 drill?**
The nearest metric drill is 0.85 mm, 0.012 mm larger. The other close size is 0.8 mm.

**Which fractional drill is closest to #66?**
1/32 in (0.0312 in) is the closest, 0.0018 in smaller.

Source page: https://machinistcharts.com/drill-size/number-66/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)