# 13/16" drill size

A 13/16 in drill is 0.8125 in (20.64 mm). It is the standard tap drill for 7/8-14 UNF; the nearest metric drill is 20.6 mm.

## 13/16" drill data

- Series: Fractional drill
- Decimal: 0.8125 in
- Metric: 20.64 mm (20.6375 mm exact)
- Nearest metric drill: 20.6 mm (−0.037 mm)
- Standard tap drill for: 7/8-14 UNF

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 20.6 mm | 0.8110 | −0.037 mm |
| 20.7 mm | 0.8150 | +0.062 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| #1 | Number | 0.2280 | 5.79 |
| Letter Z | Letter | 0.4130 | 10.49 |
| 51/64" | Fractional | 0.7969 | 20.24 |
| 13/16" | Fractional | 0.8125 | 20.64 |
| 53/64" | Fractional | 0.8281 | 21.03 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| 7/8-14 UNF | 13/16 | 67 |
| M22 × 1.5 | 20.5 mm | 70 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| M18 bolt | 18 mm | 2.64 mm | 1.32 mm | Normal fit (normal 20, loose 21 mm) |
| 3/4" bolt | 0.7500" | 0.0625" | 0.0312" | – |
| M20 bolt | 20 mm | 0.64 mm | 0.32 mm | Tighter than close fit (21 mm) |


## FAQ

**What size is a 13/16 in drill?**
A 13/16 in drill is 0.8125 in, which is 20.64 mm (20.6375 mm exactly).

**What is the metric equivalent of a 13/16 in drill?**
The nearest metric drill is 20.6 mm, 0.037 mm smaller. The other close size is 20.7 mm.

**What tap uses a 13/16 in drill?**
A 13/16 in drill is the standard tap drill for 7/8-14 UNF (about 67 % thread).

**What does a 13/16 in drill clear?**
It clears a M20 bolt with 0.64 mm total clearance (0.32 mm per side); for metric bolts: tighter than close fit.

Source page: https://machinistcharts.com/drill-size/13-16-inch/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)