Convert standard inch wrenches and sockets to millimeters, then see whether the closest size will actually fit. A 7/16" wrench is close to 11 mm. A 3/8" wrench on a 10 mm fastener is a mismatch that can round the corners.
SAE sizes
Metric sizes
Exact size
11.11 mm·7/16"
Closest metric wrench
11 mm
0.11 mm undersize
Close enough for most work. Still prefer the matching standard when you can.
Closest SAE wrench
7/16"
Exact match
Matches closely. Safe to use as the same size.
Closest is not always interchangeable. A 3/8" wrench on a 10 mm fastener can round the corners.
7/16 inch is 11.11 mm. The closest metric wrench is 11 mm, which is close enough for most work but not a perfect match.
No. 3/8 inch is 9.53 mm, so a 10 mm wrench is about 0.5 mm oversize and will often round the fastener. Use a 3/8" wrench.
Only when the sizes are nearly identical, such as 5/16" and 8 mm. Many “close” pairs are not interchangeable. Use the fit rating on this chart before you swap standards.
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