# #4 drill size

A #4 drill is 0.2090 in (5.31 mm). It sits between #5 and #3 in the number series; the nearest metric drill is 5.3 mm.

## #4 drill data

- Series: Number drill
- Decimal: 0.2090 in
- Metric: 5.31 mm (5.3086 mm exact)
- Nearest metric drill: 5.3 mm (−0.009 mm)
- Nearest fractional: 13/64" (0.2031 in)

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 5.3 mm | 0.2087 | −0.009 mm |
| 5.4 mm | 0.2126 | +0.091 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| 13/64" | Fractional | 0.2031 | 5.16 |
| #5 | Number | 0.2055 | 5.22 |
| #4 | Number | 0.2090 | 5.31 |
| #3 | Number | 0.2130 | 5.41 |
| 7/32" | Fractional | 0.2188 | 5.56 |
| Letter A | Letter | 0.2340 | 5.94 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| M6 × 0.75 | 5.2 mm | 71 |
| 1/4-20 UNC | #7 | 63 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| #8 screw | 0.1640" | 0.0450" | 0.0225" | – |
| #10 screw | 0.1900" | 0.0190" | 0.0095" | – |
| M5 bolt | 5 mm | 0.31 mm | 0.15 mm | Close fit (close 5.3, normal 5.5 mm) |


## FAQ

**What size is a #4 drill?**
A #4 drill is 0.2090 in, which is 5.31 mm (5.3086 mm exactly).

**What is the metric equivalent of a #4 drill?**
The nearest metric drill is 5.3 mm, 0.009 mm smaller. The other close size is 5.4 mm.

**What thread can I tap with a #4 drill?**
It leaves about 71 % thread in M6 × 0.75 and 63 % in 1/4-20 UNC.

**Which fractional drill is closest to #4?**
13/64 in (0.2031 in) is the closest, 0.0059 in smaller.

**What does a #4 drill clear?**
It clears a M5 bolt with 0.31 mm total clearance (0.15 mm per side); for metric bolts: close fit.

Source page: https://machinistcharts.com/drill-size/number-4/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)