Convert any drill bit size instantly with our detailed size charts. From fractional inches to millimeters, letter sizes to number sizes - get all the measurements you need for perfect holes every time. Free printable reference guides included.
| Fractional Inches | Decimal Inches | Millimeters | Closest Letter Size |
|---|---|---|---|
| 1/16" | 0.0625" | 1.5875 mm | - |
| 1/8" | 0.125" | 3.175 mm | - |
| 1/4" | 0.250" | 6.35 mm | F |
| Millimeters (mm) | Inches | Common Uses | Calculation Page |
|---|---|---|---|
| 3 mm | 0.1181 inches | Small precision holes, pilot holes | View Calculation |
| 6 mm | 0.2362 inches | General purpose, wood screws | View Calculation |
| 8 mm | 0.3150 inches | Medium bolts, dowels | View Calculation |
| 10 mm | 0.3937 inches | Large bolts, construction | View Calculation |
| 12 mm | 0.4724 inches | Heavy duty fasteners | View Calculation |
| 16 mm | 0.6299 inches | Construction anchors | View Calculation |
| 20 mm | 0.7874 inches | Large structural bolts | View Calculation |
| 25 mm | 0.9843 inches | Heavy construction | View Calculation |
| Inches | Millimeters (mm) | Common Uses | Calculation Page |
|---|---|---|---|
| 1/8 inches | 3.18 mm | Small wood screws | View Calculation |
| 1/4 inches | 6.35 mm | General purpose | View Calculation |
| 3/8 inches | 9.53 mm | Medium bolts | View Calculation |
| 1/2 inches | 12.70 mm | Large fasteners | View Calculation |
| 5/8 inches | 15.88 mm | Heavy duty bolts | View Calculation |
| 3/4 inches | 19.05 mm | Construction bolts | View Calculation |
| 1 inches | 25.40 mm | Large construction | View Calculation |
Cutting speed (CS) is measured in Surface Feet per Minute (SFM) and is calculated using:
CS = (p × D × RPM) / 12
Where:
| Material | SFM Range | Notes |
|---|---|---|
| Mild Steel | 60-100 | Use lower range for harder steels |
| Aluminum | 200-300 | Higher speeds possible with cooling |
| Screw Size | Drill Size | Decimal Equivalent |
|---|---|---|
| #4-40 | #43 | 0.089" |
Drill Bit Calculator
Copyright 2024 - © Drill Bit Calculator