Here’s a simplified way to convert between US inches and metric millimeters for wrench and spanner sizes:
Conversion Formula
- From Inches to Millimeters: Multiply by 25.4
- From Millimeters to Inches: Divide by 25.4
| Standard SAE US Wrench/Spanner Size (inches) | Metric Wrench/Spanner Size (mm) |
|---|---|
| 1/8 | 3.18 |
| 5/32 | 3.97 |
| 4 | |
| 3/16 | 4.76 |
| 5 | |
| 13/64 | 5.16 |
| 7/32 | 5.56 |
| 15/64 | 6.05 |
| 6 | |
| 1/4 | 6.35 |
| 17/64 | 6.75 |
| 7 | |
| 9/32 | 7.14 |
| 5/16 | 7.94 |
| 8 | |
| 11/32 | 8.73 |
| 9 | |
| 3/8 | 9.53 |
| 10 | |
| 11 | |
| 7/16 | 11.11 |
| 15/32 | 11.91 |
| 12 | |
| 1/2 | 12.70 |
| 13 | |
| 17/32 | 13.49 |
| 14 | |
| 9/16 | 14.29 |
| 15 | |
| 19/32 | 15.08 |
| 5/8 | 15.88 |
| 16 | |
| 21/32 | 16.67 |
| 17 | |
| 11/16 | 17.46 |
| 18 | |
| 19 | |
| 3/4 | 19.05 |
| 25/32 | 19.84 |
| 20 | |
| 13/16 | 20.64 |
| 21 | |
| 22 | |
| 7/8 | 22.23 |
| 23 | |
| 29/32 | 23.02 |
| 15/16 | 23.81 |
| 24 | |
| 31/32 | 24.61 |
| 25 | |
| 1 | 25.40 |
| 26 |
Quick Guide
- To convert an inch size to millimeters, multiply the inch size by 25.4.
- To convert a metric size to inches, divide the millimeter size by 25.4.
For example:
- 3/4 inch is approximately 0.75×25.4≈19.050.75 \times 25.4 \approx 19.050.75×25.4≈19.05 mm.
- 19 mm is approximately 19÷25.4≈0.74819 \div 25.4 \approx 0.74819÷25.4≈0.748 inches.
You can use these conversions to find the closest size if you're working with a range of available tools, like wrenches and sockets.
