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" at a glance
Decimal, metric and the nearest sizes in the other series.
- Decimal inch
- 0.8125"
- Millimetres
- 20.64 mm 20.6375
- Nearest metric drill
- 20.6 mm −0.037 mm
- Hole area
- 0.518 in² 334.5 mm²
- Tap drill for
- 7/8-14 UNF
Nearest metric drills
Metric drills step by 0.05 mm below 3 mm and by 0.1 mm from 3 mm. Difference is metric minus inch size.
| Metric drill | Inch | Difference | In inches | Hole |
|---|---|---|---|---|
| 20.6 mm | 0.8110" | −0.037 mm | −0.0015" | Smaller |
| 20.7 mm | 0.8150" | +0.062 mm | +0.0025" | Larger |
Nearby inch drills
The next size down and up in each inch series, so you can pick a substitute from the drawer.
Threads a 13/16" drill can tap
Threads from the tap tables on this site that this drill can tap, with the thread percentage it leaves (55–85 % shown).
| Thread | Standard drill | Thread with this drill | Suits |
|---|---|---|---|
| 7/8-14 UNF | 13/16 | 67 % | Standard drill |
| M22 × 1.5 | 20.5 mm | 70 % | Good in steel |
Clearance for screws and bolts
Bolts and screws a 13/16" hole clears, with the diametral clearance and the gap each side. Metric sizes are compared with ISO 273.
| Fastener | Diameter | Clearance | Per side | ISO 273, metric only |
|---|---|---|---|---|
| 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) |
Inch clearance is the drill size minus the basic major diameter. A drilled hole usually cuts slightly oversize.
Fractional drill index
Every size in the series, holes drawn to scale.
Common questions
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.