Metric Charts • Standard Charts

Welcome to Socket Size where we strive to help you get the most utility from your sockets and wrenches. Do you find converting sockets between metric and standard measurement sizes confusing? We can help!

Socket conversions between metric and standard can be confusing if you are familiar with one measurement system but not the other. SocketSize.com can help with that, and many other fastener, socket and wrench related challenges. Thanks for visiting.

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Standard sockets vs Metric nuts and bolts

Metric fasteners including nuts and bolts are measured by the millimeter(mm). Tightening or loosening a metric fastener can be a challenge if you only have standard sockets, which are measured in inches. There is no exact match between metric and standard socket sizes, however, this conversion chart should help you identify the closest match.

Metric Fastener SizeClosest Standard Socket
4 mmuse a 3/16" socket
5 mmuse a 1/4" socket
6 mmuse a 1/4" socket
7 mmuse a 5/16" socket
8 mmuse a 3/8" socket
9 mmuse a 3/8" socket
10 mmuse a 7/16" socket
11 mmuse a 7/16" socket
12 mmuse a 1/2" socket
13 mmuse a 9/16" socket
14 mmuse a 9/16" socket
15 mmuse a 5/8" socket
16 mmuse a 11/16" socket
17 mmuse a 11/16" socket
18 mmuse a 3/4" socket
19 mmuse a 3/4" socket
20 mmuse a 13/16" socket
21 mmuse a 7/8" socket
22 mmuse a 7/8" socket
23 mmuse a 15/16" socket
24 mmuse a 1" socket
25 mmuse a 1" socket
26 mmuse a 1 1/16" socket
27 mmuse a 1 1/8" socket
28 mmuse a 1 1/8" socket
29 mmuse a 1 1/4" socket
30 mmuse a 1 1/4" socket
31 mmuse a 1 1/4" socket
32 mmuse a 1 5/16" socket
33 mmuse a 1 5/16" socket
34 mmuse a 1 3/8" socket
35 mmuse a 1 7/16" socket
36 mmuse a 1 7/16" socket
37 mmuse a 1 1/2" socket
38 mmuse a 1 1/2" socket
39 mmuse a 1 9/16" socket
40 mmuse a 1 5/8" socket
41 mmuse a 1 5/8" socket
42 mmuse a 1 11/16" socket
43 mmuse a 1 3/4" socket
44 mmuse a 1 3/4" socket
45 mmuse a 1 13/16" socket
46 mmuse a 1 13/16" socket
47 mmuse a 1 7/8" socket
48 mmuse a 1 15/16" socket
49 mmuse a 1 15/16" socket
50 mmuse a 2" socket

Remember, these are not metric vs standard measurement charts, they are metric vs standard SOCKET SIZE conversion charts. Metric and Standard socket types don't have exact conversions in terms of size.

You need to use a socket or wrench that is slightly larger when using one type of socket on a nut, bolt, screw or fastener of the opposite type.

Metric sockets vs Standard fasteners

Standard fasteners are measured in inches. Tightening or loosening a standard fastener can be a challenge with metric sockets. There is no exact match between standard and metric socket sizes but the conversion chart below will help you choose the right socket.

Standard Fastener SizeClosest Metric Socket
1/8 inchuse a 4 mm socket
3/16 inchuse a 5 mm socket
1/4 inchuse a 7 mm socket
5/16 inchuse an 8 mm socket
3/8 inchuse a 10 mm socket
7/16 inchuse a 12 mm socket
1/2 inchuse a 13 mm socket
9/16 inchuse a 15 mm socket
5/8 inchuse a 16 mm socket
11/16 inchuse an 18 mm socket
3/4 inchuse a 20 mm socket
13/16 inchuse a 21 mm socket
7/8 inchuse a 23 mm socket
15/16 inchuse a 24 mm socket
1 inchuse a 26 mm socket
1 1/8 inchuse a 29 mm socket
1 3/16 inchuse a 31 mm socket
1 1/4 inchuse a 32 mm socket
1 5/16 inchuse a 34 mm socket
1 3/8 inchuse a 35 mm socket
1 7/16 inchuse a 37 mm socket
1 1/2 inchuse a 39 mm socket
1 9/16 inchuse a 40 mm socket
1 5/8 inchuse a 42 mm socket
1 11/16 inchuse a 43 mm socket
1 3/4 inchuse a 45 mm socket
1 13/16 inchuse a 47 mm socket
1 7/8 inchuse a 48 mm socket
1 15/16 inchuse a 50 mm socket
2 inchuse a 51 mm socket
2 1/8 inchuse a 54 mm socket
2 3/16 inchuse a 56 mm socket
2 1/4 inchuse a 58 mm socket
2 5/16 inchuse a 59 mm socket
2 3/8 inchuse a 61 mm socket
2 7/16 inchuse a 62 mm socket
2 1/2 inchuse a 64 mm socket
2 9/16 inchuse a 66 mm socket
2 5/8 inchuse a 67 mm socket
2 11/16 inchuse a 69 mm socket
2 3/4 inchuse a 70 mm socket
2 13/16 inchuse a 72 mm socket
2 7/8 inchuse a 74 mm socket
2 15/16 inchuse a 75 mm socket

The Metric to Standard and Standard to Metric socket conversion charts above work for all socket ratchet sizes(1/4, 3/8, 1/2, 3/4 and 1 inch) as well as all socket types(6-point, 12-point, hex, impact etc). The two charts below show all the socket sizes in each of the five most common socket sets.

Metric Socket Size Chart

1/4” Socket Set3/8” Socket Set1/2” Socket Set3/4” Socket Set1” Socket Set
4 mm5.5 mm8 mm19 mm36 mm
4.5 mm6 mm9 mm20 mm38 mm
5 mm7 mm10 mm21 mm41 mm
5.5 mm8 mm11 mm22 mm46 mm
6 mm9 mm12 mm23 mm50 mm
7 mm10 mm13 mm24 mm54 mm
8 mm11 mm14 mm25 mm55 mm
9 mm12 mm15 mm26 mm58 mm
10 mm13 mm16 mm27 mm60 mm
11 mm14 mm17 mm28 mm63 mm
12 mm15 mm18 mm29 mm65 mm
13 mm16 mm19 mm30 mm67 mm
14 mm17 mm20 mm31 mm70 mm
15 mm18 mm21 mm32 mm71 mm
19 mm22 mm33 mm75 mm
20 mm23 mm34 mm77 mm
21 mm24 mm35 mm80 mm
22 mm25 mm36 mm
26 mm38 mm
27 mm40 mm
28 mm41 mm
30 mm42 mm

The socket set sizes chart above and below tell you which sockets are included with each driver size.

A socket adapter can make sockets of one set work with the driver of another set regardless of size difference. Additionally each set may contain drivers and sockets from multiple sets for convenience.

SAE Socket Sizes Chart

1/4” Socket Set3/8” Socket Set1/2” Socket Set3/4” Soket Set1” Socket Set
5/32 inch1/4 inch3/8 inch7/8 inch1-5/8 inch
3/16 inch5/16 inch7/16 inch15/16 inch1-11/16 inch
7/32 inch3/8 inch1/2 inch1 inch1-3/4 inch
1/4 inch7/16 inch9/16 inch1-1/16 inch1-13/16 inch
9/32 inch1/2 inch19/32 inch1-1/8 inch1-7/8 inch
5/16 inch9/16 inch5/8 inch1-3/16 inch2 inch
11/32 inch5/8 inch21/32 inch21/32 inch2-1/8 inch
3/8 inch11/16 inch11/16 inch1-5/16 inch2-3/16 inch
7/16 inch3/4 inch3/4 inch1-3/8 inch2-1/4 inch
1/2 inch13/16 inch25/32 inch1-7/16 inch2-3/8 inch
9/16 inch7/8 inch13/16 inch1-1/2 inch2-1/2 inch
15/16 inch7/8 inch1-5/8 inch2-5/8 inch
1 inch15/16 inch1-11/16 inch2-3/4 inch
1 inch1-3/4 inch2-15/16 inch
1-1/16 inch1-13/16 inch3 inch
1-1/8”1-7/8”3-1/8”
1-3/16 inch2 inch
1-1/4”2-1/8”
1-1/2 inch2-3/16 inch
2-1/4”

Frequently asked questions

These are some of the more commonly asked questions about standard vs metric socket use.

Is SAE Standard or Metric?

SAE stands for "Society of Automotive Engineers". The society of automotive engineers standardized the use of inches and fractions of inches when measuring nuts and bolts on vehicles built in America circa 1970. SAE is standard and measured in inches.

What is the difference between standard and metric sockets?

The difference between standard and metric sockets is the measurement system they use and, correspondingly, the sizes they are. A standard socket is measured and sized in inches whereas a metric socket is measured and sized in millimeters(mm).

How do I know what size socket I have?

Socket size is marked on the side of each socket. On metric sockets it will be marked in millimeters, example: 10mm. On standard sockets it will be marked in inches and fractions of inches. Example: 1 1/4in.

Sockets that don't have a size marked on the side can be measured by seeing how wide the space is inside the socket, or by finding a bolt or nut with a known size that the socket fits over snugly.

How do I know what size ratchet I need?

The size of ratchet needed for any particular socket is determined by the size of the square connecting end of the socket. Smaller sockets will have a square opening as small as 1/4 inch while larger sockets have a square opening of up to 1 inch. The ratchet drive must be of the same size as the square end of the socket or it will not fit.

Note: A socket adapter can be used to allow a ratchet drive to work on a socket designed for a different ratchet size. Also, only the square end of a socket should connect to a ratchet. The 6 and 12 point end of the socket is for grasping fasteners like nuts and bolts.

What is the most common ratchet size?

The most common ratchet size for home use is the 3/8 inch drive ratchet followed closely by the 1/4 inch drive and 1/2 inch drive ratchets. It should be noted that different tasks will require different socket sizes based on the fastener size of the object being worked on. Small engines, for example, use smaller bolts than larger vehicle engines.

Warning: Using a socket of the wrong measurement type on a fastener can damage the fastener, especially if the fastener is already worn, rusted or stuck. These charts are provided to help you identify the closest socket size from a different measurement system , however, it is recommended you always use the right socket size on any fastener whenever possible.

Using standard sockets on metric bolts, and vice versa, can work but there is an increased risk of rounding, stripping or breaking the fasterner. Always use caution, even with the right tools.

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