---
type: "drill"
designation: "11/32"
series: "fractional"
series_name: "Fractional Drill Sizes"
diameter_in: 0.34375
diameter_mm: 8.73125
fraction_label: "11/32"
standard: "ANSI/ASME B94.11M; BS 328"
verified: "August 1, 2026"
url: https://shopmath.org/drills/fractional/11-32
---

# 11/32 Drill Bit Size — 0.3438 in / 8.731 mm

A 11/32 drill bit is 0.3438 in (8.731 mm) in diameter. It belongs to the fractional series of standard twist drills. It is the recommended tap drill for 1/8-27 NPT, 1/8-27 NPTF, 3/8"-32 UNEF.

- **Designation**: 11/32
- **Series**: Fractional
- **Diameter**: 0.3438 in (8.731 mm)
- **Fraction**: 11/32

## 11/32 Drill Diameter

| Property | Value |
| --- | --- |
| Designation | 11/32 |
| Series | Fractional |
| Diameter (in) | 0.3438 |
| Diameter (mm) | 8.731 |
| Fractional call-out | 11/32 |

## 11/32 Drill Equivalents in the Other Size Series

The nearest standard drill to 11/32 in each of the other three series. Nothing here is an exact match unless the difference column reads 0.0000 in.

| Series | Nearest drill | Diameter (in) | Diameter (mm) | Difference |
| --- | --- | --- | --- | --- |
| Number | [#1](https://shopmath.org/drills/number/1.md) | 0.2280 | 5.791 | -0.1157 in |
| Letter | [S](https://shopmath.org/drills/letter/s.md) | 0.3480 | 8.839 | +0.0042 in |
| Metric | [8.7 mm](https://shopmath.org/drills/metric/8-7mm.md) | 0.3425 | 8.700 | -0.0012 in |

## Threads Tapped With a 11/32 Drill

| Thread | Pitch | Thread engagement (%) |
| --- | --- | --- |
| [1/8-27 NPT](https://shopmath.org/threads/npt/1-8.md) | 27 TPI | — |
| [1/8-27 NPTF](https://shopmath.org/threads/nptf/1-8.md) | 27 TPI | — |
| [3/8"-32 UNEF](https://shopmath.org/threads/unef/3-8-32.md) | 32 TPI | 77.0 |

_Engagement is what the real drill leaves with a cut tap, not the requested target._

## Sources and Method for the 11/32 Drill Size

### Drill index

- **Source**: Number/letter: bd_warehouse drill_sizes.csv (Apache-2.0) cross-checked against Wikipedia Drill bit sizes (CC BY-SA 4.0). Fractional: computed 1/64 in steps per ANSI B94.11M. Metric: computed BS 328 increment pattern.
- **Method**: computed
- **Verified against**: Wikipedia Drill bit sizes (CC BY-SA 4.0); 31/31 checks passed

### Assumptions

- Drill diameters are nominal. A worn or run-out drill cuts oversize; measure the hole, not the shank, when the fit matters.
- Dataset scope: Number sizes #61-#80 are stored but tagged demandTier 'extended' — query-space-map.md Appendix A found the tail thinning in the 60s. Sizes below #80 and metric sizes above 25.0 mm excluded.

**Data last verified**: August 1, 2026

## Common Questions About the 11/32 Drill Bit

### What size is a 11/32 drill bit size?

A 11/32 drill bit is 0.3438 in (8.731 mm) in diameter. The nearest fractional call-out is 11/32.

### What is the metric equivalent of a 11/32 drill bit?

The closest metric drill to 11/32 (0.3438 in (8.731 mm)) is 8.7 mm at 0.3425 in (8.700 mm) — a difference of 0.0012 in.

### What thread does a 11/32 drill bit tap?

A 11/32 drill is the recommended tap drill for 1/8-27 NPT, 1/8-27 NPTF, 3/8"-32 UNEF. Each leaves the thread engagement shown in the table above with a cut tap.

## Related pages

- Next size down (any series): [8.7 mm](https://shopmath.org/drills/metric/8-7mm.md) — 0.3425 in (8.700 mm)
- Next size up (any series): [8.8 mm](https://shopmath.org/drills/metric/8-8mm.md) — 0.3465 in (8.800 mm)
- Previous in the fractional series: [21/64](https://shopmath.org/drills/fractional/21-64.md)
- Next in the fractional series: [23/64](https://shopmath.org/drills/fractional/23-64.md)
- All fractional sizes: [Fractional drill sizes](https://shopmath.org/drills/fractional.md)
- All drill sizes: [Drill bit size reference](https://shopmath.org/drills.md)
- Complete index by diameter: [Drill size chart](https://shopmath.org/charts/drill-sizes.md)
- Tap drills by thread: [Tap drill chart](https://shopmath.org/charts/tap-drill.md)

---

*Source: [ShopMath](https://shopmath.org/drills/fractional/11-32) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*