Wrench Socket Conversions Chart SAE Metric Spanner

Wrench Conversion Chart for SAE & Metric Sizes

Wrench Conversion Chart SAE Metric Sizes

SAE & Metric Wrench Conversions

SAE Wrench Size Bolt Size (SI) Metric Wrench Size
5/16″ 1/8″ 8 mm
3/8″ 3/16″ 10 mm
7/16″ 1/4″ 11 mm
1/2″ 5/16″ 13 mm
9/16″ 3/8″ 14 mm
5/8″ 7/16″ 16 mm
3/4″ 1/2″ 19 mm
13/16″ 9/16″ 21 mm
7/8″ 9/16″ 22 mm
15/16″ 5/8″ 24 mm


If you live in the U.S., chances are you have more SAE wrenches in your tool box. And for our international readers, you likely have more metric wrenches in yours. Whatever the case may be, our wrench conversion chart will give you the best-fitting standard or metric wrench for a given bolt size. Unlike screws, nuts & bolts are less prone to stripping when being fastened with a substitute wrench. Thus, there’s less risk involved when trying a wrench’s metric or SAE equivalent. And, you can save time and money by not having to leave the job to purchase another wrench. With that being said, it’s generally safer and more efficient to use SAE wrenches with SAE bolt sizes and metric wrenches on metric hardware.

When reading our wrench conversion chart, start with the bolt that you are fastening. From there, look at the options you have for both SAE and metric wrenches. In instance like bolt size, 9/16″, there are two different possible wrench fittings on either measurement scale. If you encounter this, your may need to experience with all four potential wrench sizes. Chances are that there will be two eligible wrench sizes that you can use (1 SAE & 1 MM).

Sizing Wrenches for Metric Bolts

If you’re looking to find the right wrench for a metric bolt, the conversion is very much the same. Once you’ve identified which metric wrench you would use, look at the chart to locate its SAE counterpart. Now, we do realize that the chart doesn’t look complete on the metric side. However, the only common wrench size that isn’t included in the chart is 18 mm, and it’s counterpart is 45/64″. If you don’t have that size, don’t worry—neither do we.

Converting Smaller Wrench Sizes

Didn’t see the spanner size you were looking for? No worries! We have both metric to SAE and SAE to metric conversion charts for hex keys. Be sure to read the instructions as smaller wrenches are more difficult to substitute for one another. Also, smaller pieces of hardware are more prone to getting stripped or damaged.

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