# #78 drill size

A #78 drill is 0.0160 in (0.41 mm). It sits between #79 and #77 in the number series; the nearest metric drill is 0.4 mm.

## #78 drill data

- Series: Number drill
- Decimal: 0.0160 in
- Metric: 0.41 mm (0.4064 mm exact)
- Nearest metric drill: 0.4 mm (−0.006 mm)
- Nearest fractional: 1/64" (0.0156 in)

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 0.4 mm | 0.0157 | −0.006 mm |
| 0.45 mm | 0.0177 | +0.044 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| #79 | Number | 0.0145 | 0.37 |
| 1/64" | Fractional | 0.0156 | 0.40 |
| #78 | Number | 0.0160 | 0.41 |
| #77 | Number | 0.0180 | 0.46 |
| 1/32" | Fractional | 0.0312 | 0.79 |
| Letter A | Letter | 0.2340 | 5.94 |


## FAQ

**What size is a #78 drill?**
A #78 drill is 0.0160 in, which is 0.41 mm (0.4064 mm exactly).

**What is the metric equivalent of a #78 drill?**
The nearest metric drill is 0.4 mm, 0.006 mm smaller. The other close size is 0.45 mm.

**Which fractional drill is closest to #78?**
1/64 in (0.0156 in) is the closest, 0.0004 in smaller.

Source page: https://machinistcharts.com/drill-size/number-78/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)