Drill Bit Size Chart: Fraction, Decimal & mm | TaskHolt
Drill Bit Size Chart (Fraction, Decimal & mm)
A drill bit size chart converting fractional inch, decimal inch and metric (mm) sizes — the common sizes you actually use, side by side.
Common drill bit sizes
| Fraction (in) | Decimal (in) | Metric (mm) |
|---|---|---|
| 1/16 | 0.0625 | 1.59 |
| 5/64 | 0.0781 | 1.98 |
| 3/32 | 0.0938 | 2.38 |
| 1/8 | 0.125 | 3.18 |
| 9/64 | 0.1406 | 3.57 |
| 5/32 | 0.1563 | 3.97 |
| 3/16 | 0.1875 | 4.76 |
| 7/32 | 0.2188 | 5.56 |
| 1/4 | 0.250 | 6.35 |
| 5/16 | 0.3125 | 7.94 |
| 3/8 | 0.375 | 9.53 |
| 7/16 | 0.4375 | 11.11 |
| 1/2 | 0.500 | 12.70 |
| 9/16 | 0.5625 | 14.29 |
| 5/8 | 0.625 | 15.88 |
| 3/4 | 0.750 | 19.05 |
| 1 | 1.000 | 25.40 |
To convert: decimal inch × 25.4 = mm. For threaded holes use a tap & drill chart instead, which gives the correct undersized bit for each thread.
Frequently asked questions
How do I convert drill bit sizes to mm?
Multiply the decimal inch size by 25.4. For example, 1/4 in = 0.25 × 25.4 = 6.35 mm.
What is the most common drill bit size?
For general household use, 1/8 in (3.18 mm) and 1/4 in (6.35 mm) are the most used. A basic set spans 1/16 in to 1/2 in.