Converting between metric and standard (SAE) wrench sizes is a common task when working with fasteners from different systems. This chart provides a quick reference for matching metric wrench sizes to their closest standard (inch-based) equivalents. It’s a practical tool for mechanics, technicians, and anyone who regularly works with both measurement systems.
| Metric Size (mm) | Closest Standard Size | Decimal Equivalent | Difference |
|---|---|---|---|
| 3.18mm | 1/8″ | 0.125″ | +0.000″ |
| 4mm | 5/32″ | 0.156″ | -0.001″ |
| 5mm | 3/16″ | 0.188″ | -0.009″ |
| 6mm | 7/32″ | 0.219″ | -0.017″ |
| 7mm | 1/4″ | 0.250″ | -0.025″ |
| 8mm | 5/16″ | 0.313″ | -0.002″ |
| 9mm | 11/32″ | 0.344″ | -0.010″ |
| 10mm | 3/8″ | 0.375″ | -0.019″ |
| 11mm | 7/16″ | 0.438″ | -0.005″ |
| 12mm | 15/32″ | 0.469″ | +0.003″ |
| 13mm | 1/2″ | 0.500″ | -0.012″ |
| 14mm | 9/16″ | 0.563″ | -0.012″ |
| 15mm | 19/32″ | 0.594″ | +0.003″ |
| 16mm | 5/8″ | 0.625″ | -0.005″ |
| 17mm | 21/32″ | 0.656″ | +0.013″ |
| 18mm | 11/16″ | 0.688″ | +0.021″ |
| 19mm | 3/4″ | 0.750″ | -0.002″ |
| 20mm | 25/32″ | 0.781″ | +0.006″ |
| 21mm | 13/16″ | 0.813″ | +0.014″ |
| 22mm | 7/8″ | 0.875″ | -0.009″ |
| 23mm | 29/32″ | 0.906″ | -0.000″ |
| 24mm | 15/16″ | 0.938″ | -0.007″ |
| 25mm | 1″ | 1.000″ | -0.016″ |
| 26mm | 1-1/32″ | 1.031″ | -0.007″ |
| 27mm | 1-1/16″ | 1.063″ | +0.001″ |
| 28mm | 1-1/8″ | 1.125″ | +0.023″ |
| 29mm | 1-5/32″ | 1.156″ | +0.014″ |
| 30mm | 1-3/16″ | 1.188″ | +0.006″ |
| 31mm | 1-7/32″ | 1.219″ | -0.002″ |
| 32mm | 1-1/4″ | 1.250″ | -0.010″ |
| 33mm | 1-19/64″ | 1.297″ | -0.002″ |
| 34mm | 1-5/16″ | 1.313″ | -0.026″ |
| 35mm | 1-3/8″ | 1.375″ | +0.003″ |
| 36mm | 1-7/16″ | 1.438″ | +0.020″ |
| 38mm | 1-1/2″ | 1.500″ | +0.004″ |
| 39mm | 1-9/16″ | 1.563″ | +0.027″ |
| 40mm | 1-9/16″ | 1.563″ | -0.012″ |
| 41mm | 1-5/8″ | 1.625″ | +0.011″ |
| 46mm | 1-13/16″ | 1.813″ | +0.001″ |
| 50mm | 2″ | 2.000″ | +0.032″ |
| 51mm | 2″ | 2.000″ | -0.008″ |
| 54mm | 2-1/8″ | 2.125″ | +0.000″ |
| 55mm | 2-5/32″ | 2.156″ | -0.009″ |
| 57mm | 2-1/4″ | 2.250″ | +0.006″ |
| 58mm | 2-9/32″ | 2.281″ | +0.000″ |
| 60mm | 2-3/8″ | 2.375″ | +0.014″ |
| 63mm | 2-1/2″ | 2.500″ | +0.020″ |
Important Notes:
- Differences: The difference column shows how much larger (+) or smaller (-) the standard size is compared to the metric size.
- Interchangeability: Sizes with differences under ±0.005″ are generally interchangeable for most applications.
- Precision: Always use the exact size when possible for critical applications or when working with precision fasteners.
- Tool Quality: Higher quality tools typically have tighter tolerances and better fit.
- Material Considerations: Softer materials (brass, aluminum) require more precise fits to avoid damage.
MISUMI USA offers a wide selection of wrenches, socket sets, and fasteners, all available with fast shipping. If you have questions about wrench or socket sizing for your next project, our product experts are here to help. Be sure to check out our MechBlog for additional articles and reference charts designed to support engineers and manufacturers as they navigate common challenges.
Author: Scott Bredemann | Updated: 6/6/2025
Disclaimer
The content on this webpage is for informational purposes only. MISUMI makes no guarantees, expressed or implied, regarding the accuracy, completeness, or validity of the information. Performance parameters, tolerances, designs, materials, or processes should not be assumed to reflect third-party suppliers’ or manufacturers’ deliverables within MISUMI’s network. Buyers are responsible for specifying their part requirements