1" drill size
A 1 in drill is 1.0000 in (25.40 mm). It is the largest fractional drill on this chart; the nearest metric drill is 25.4 mm.
1" at a glance
Decimal, metric and the nearest sizes in the other series.
- Decimal inch
- 1.0000"
- Millimetres
- 25.40 mm 25.4000
- Series
- Fractional next to 63/64"
- Nearest metric drill
- 25.4 mm 0 mm
- Hole area
- 0.785 in² 506.7 mm²
- Tap drill for
- Not a standard tap drill on this site
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 |
|---|---|---|---|---|
| 25.3 mm | 0.9961" | −0.100 mm | −0.0039" | Smaller |
| 25.4 mm | 1.0000" | 0 mm | 0" | Same size |
Nearby inch drills
The next size down and up in each inch series, so you can pick a substitute from the drawer.
Threads a 1" 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 |
|---|---|---|---|
| M27 × 2 | 25 mm | 62 % | Hard, tough metals |
Clearance for screws and bolts
Bolts and screws a 1" 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 |
|---|---|---|---|---|
| M22 bolt | 22 mm | 3.40 mm | 1.70 mm | Normal fit (normal 24, loose 26 mm) |
| M24 bolt | 24 mm | 1.40 mm | 0.70 mm | Close fit (close 25, normal 26 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 1 in drill?
A 1 in drill is 1.0000 in, which is 25.40 mm (25.4000 mm exactly).
What is the metric equivalent of a 1 in drill?
The nearest metric drill is 25.4 mm, 0.000 mm smaller. The other close size is 25.3 mm.
What thread can I tap with a 1 in drill?
It leaves about 62 % thread in M27 × 2.
What does a 1 in drill clear?
It clears a M24 bolt with 1.40 mm total clearance (0.70 mm per side); for metric bolts: close fit.