SAE to Metric Conversions for Hex Keys Chart Image

SAE to Metric Conversions for Hex Keys

SAE to Metric Conversion for Hexy Keys Allen Wrenches

SAE to Metric Conversions for Hex Keys Chart

SAE Hex Key Metric Hex Size
5/64″ 2 mm
3/32″ 2.5 mm
7/64″ 3 mm
1/8″ 3.5 mm
5/32″ 4 mm
3/16″ 5 mm
7/32″ 5.5 mm & 6 mm
1/4″ 7 mm
5/16 “ 8 mm
3/8″ 10 mm


If you’re looking for a quick imperial to metric conversion guide for Allen wrenches, you’ve come to the right place. We’ve provided the best substitute SAE hex key for each given metric size. But before you choose to reference this chart, you must know that we always recommend that you upgrade to a separate metric hex key set. With more and more hardware being produced overseas, both SAE and metric hex key sets will be staples in your tool box.

Now let’s move on to the SAE to Metric Conversions for Hex Keys chart. When you reference the hex key chart above, do be aware that using a smaller size bit will increase you vulnerability for stripping your hardware. In some cases, you may want to try using a size above the one recommended in the chart to see if it fits by chance. Also, we will caution you that smaller screw sizes are more prone to stripping so be extra careful when working with precision hardware. Lastly, please remember that not every metric size has a perfect SAE counterpart. If you need a substitute for a metric size like 9 mm, you’re only option might be to get a metric set with that wrench size. In any case, we hope you find this chart helpful and feel free to pass it along to other tool fanatics!

Looking for a metric to SAE conversion chart for hex keys? We have you covered! Checkout our hex key conversions guide for both metric & SAE. This guide includes both the information above plus their reverse counter parts. When you look at both the SAE to metric guide & the metric to SAE guide next to each other, you’ll notice that most conversions are not a two-way substitution. Thus, we added both to clarify any confusion. Enjoy!

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