Utility Loft → Socket Size → Metric to Standard

Metric to Standard Conversion

Find the closest SAE (inch) size for any metric (mm) socket or wrench, and see how tight the match is. Convert a single size below.

Your metric size (mm)

Enter a metric size above to find the closest SAE (inch) wrench.

Metric to SAE chart

Metric	Closest SAE	SAE width	Difference	Fit
4 mm	5/32"	3.97 mm	-0.03 mm	≈ exact
4.5 mm	3/16"	4.76 mm	+0.26 mm	close
5 mm	3/16"	4.76 mm	-0.24 mm	close
5.5 mm	7/32"	5.56 mm	+0.06 mm	≈ exact
6 mm	1/4"	6.35 mm	+0.35 mm	close
7 mm	9/32"	7.14 mm	+0.14 mm	≈ exact
8 mm	5/16"	7.94 mm	-0.06 mm	≈ exact
9 mm	11/32"	8.73 mm	-0.27 mm	close
10 mm	3/8"	9.53 mm	-0.47 mm	loose
11 mm	7/16"	11.11 mm	+0.11 mm	≈ exact
12 mm	1/2"	12.70 mm	+0.70 mm	loose
13 mm	1/2"	12.70 mm	-0.30 mm	close
14 mm	9/16"	14.29 mm	+0.29 mm	close
15 mm	9/16"	14.29 mm	-0.71 mm	loose
16 mm	5/8"	15.88 mm	-0.12 mm	≈ exact
17 mm	11/16"	17.46 mm	+0.46 mm	loose
18 mm	11/16"	17.46 mm	-0.54 mm	loose
19 mm	3/4"	19.05 mm	+0.05 mm	≈ exact
20 mm	13/16"	20.64 mm	+0.64 mm	loose
21 mm	13/16"	20.64 mm	-0.36 mm	close
22 mm	7/8"	22.23 mm	+0.23 mm	close
24 mm	15/16"	23.81 mm	-0.19 mm	≈ exact
27 mm	1-1/16"	26.99 mm	-0.01 mm	≈ exact
30 mm	1-1/8"	28.58 mm	-1.42 mm	loose
32 mm	1-1/4"	31.75 mm	-0.25 mm	close

A positive difference means the SAE size is larger. Loose matches can round a fastener — use a metric socket for tight metric bolts.

What is 10mm in standard?

10 mm is closest to 3/8 inch (9.53 mm), about 0.5 mm smaller, so it's a loose match — there's no exact SAE equivalent to 10 mm.

What is 13mm in standard?

13 mm is closest to 1/2 inch (12.7 mm), just 0.3 mm smaller — a close, usable match.

What is 19mm in standard?

19 mm is almost exactly 3/4 inch (19.05 mm) — the two are interchangeable in practice.