1/8 inch Drill Bit Size
A 1/8 inch drill bit is 0.1250 inches or 3.18 mm. It is one of the most common small pilot-hole and general-purpose drill sizes.
Quick Answer
Decimal
0.1250 in
Metric
3.18 mm
Closest
3 mm
1/8 inch Drill Bit Equivalent Chart
| Size | Decimal Inches | Metric | Note |
|---|---|---|---|
| 1/8 inch | 0.1250 in | 3.18 mm | Exact size |
| 3 mm | 0.1181 in | 3.00 mm | Common metric undersize |
| #30 | 0.1285 in | 3.26 mm | Nearby numbered drill size |
| 7/64 inch | 0.1094 in | 2.78 mm | Smaller pilot-hole option |
Common Uses
Pilot holes for #6 to #8 screws, small anchors, and general drilling.
Exact vs Nearest Size
Choose the exact bit for threads, tight hardware fits, dowels, and precision layouts. Use the nearest common equivalent only for rough pilot holes, clearance holes, or material removal where a slight difference is acceptable.
1/8 inch Drill Bit FAQ
What are the inch and metric dimensions for 1/8 inch?
1/8 inch drill bit measures 0.1250 in and 3.18 mm.
What is the closest common equivalent to 1/8 inch?
3 mm is the closest common equivalent listed here. It measures 0.1181 in or 3.00 mm.
Can I substitute another bit for 1/8 inch?
Use the exact bit size for tap drilling, precision holes, dowels, and manufacturer-specified hardware. A nearby fractional, metric, numbered, or letter drill bit is usually fine only for clearance holes or rough pilot holes.