# #40 drill size

A #40 drill is 0.0980 in (2.49 mm). It sits between #41 and #39 in the number series; the nearest metric drill is 2.5 mm.

## #40 drill data

- Series: Number drill
- Decimal: 0.0980 in
- Metric: 2.49 mm (2.4892 mm exact)
- Nearest metric drill: 2.5 mm (+0.011 mm)
- Nearest fractional: 3/32" (0.0938 in)

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 2.45 mm | 0.0965 | −0.039 mm |
| 2.5 mm | 0.0984 | +0.011 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| 3/32" | Fractional | 0.0938 | 2.38 |
| #41 | Number | 0.0960 | 2.44 |
| #40 | Number | 0.0980 | 2.49 |
| #39 | Number | 0.0995 | 2.53 |
| 7/64" | Fractional | 0.1094 | 2.78 |
| Letter A | Letter | 0.2340 | 5.94 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| M3 × 0.5 | 2.5 mm | 79 |
| #5-40 UNC | #38 | 83 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| #1 screw | 0.0730" | 0.0250" | 0.0125" | – |
| M2 bolt | 2 mm | 0.49 mm | 0.24 mm | Normal fit (normal 2.4, loose 2.6 mm) |
| #2 screw | 0.0860" | 0.0120" | 0.0060" | – |


## FAQ

**What size is a #40 drill?**
A #40 drill is 0.0980 in, which is 2.49 mm (2.4892 mm exactly).

**What is the metric equivalent of a #40 drill?**
The nearest metric drill is 2.5 mm, 0.011 mm larger. The other close size is 2.45 mm.

**What thread can I tap with a #40 drill?**
It leaves about 79 % thread in M3 × 0.5 and 83 % in #5-40 UNC.

**Which fractional drill is closest to #40?**
3/32 in (0.0938 in) is the closest, 0.0043 in smaller.

**What does a #40 drill clear?**
It clears a #2 screw with 0.0120" total clearance (0.0060" per side).

Source page: https://machinistcharts.com/drill-size/number-40/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)