Socket Size Chart (Metric-Imperial Equivalents)

For your convenience, here is a simplified chart of socket sizes including a cross-reference table of hex sockets across flats (and possible drive sizes) their metric (SI) and imperial (US decimal / fractional inches) values.

We trust that the information below is self-explanatory and straightforward.

Metric Socket Hex A/F Imperial Equivalent Nearest Alternative Socket Size
Metric (mm) Decimal inches Fractional inches
3.5 0.138 ---
4 0.156 5/32
4.5 0.177 ---
5 0.197 ---
5.5 0.217 7/32
6 0.236 1/4
7 0.276 ---
8 0.315 5/16
9 0.354 ---
10 0.394 3/8
11 0.433 7/16
12 0.472 1/2
13 0.512 9/16
14 0.551 5/8
15 0.591 11/16
16 0.63 3/4
17 0.669 7/8
18 0.709 15/16
19 0.748 1
20 0.787 25/32
21 0.827 ---
22 0.866 7/8
24 0.945 1
25 0.984 1
26 1.024 ---
27 1.063 1 1/8
28 1.102 ---
29 1.142 ---
30 1.181 1 3/16
31 1.22 ---
32 1.259 1 1/4
33 1.299 15/16
34 1.338 ---
35 1.378 1 3/8
36 1.417 1 3/8
37 1.457 ---
38 1.496 1 1/2
39 1.535 ---
40 1.575 1 9/16
41 1.614 1 5/8
42 1.653 ---
43 1.693 1 11/16
44 1.732 ---
45 1.772 ---
46 1.811 1 13/16
47 1.85 ---
48 1.89 ---
49 1.929 ---
50 1.968 ---
52 2.047 21/16
54 2.126 2 1/8
55 2.165 2 3/16
56 2.205 2 3/16
57 2.244 2 1/4
58 2.283 ---
60 2.362 2 3/8
62 2.441 2 7/16
63 2.48 2 1/2
65 2.559 2 9/16
67 2.638 2 5/8
70 2.756 2 3/4
75 2.953 2 15/16
80 3.15 ---
85 3.346 3 3/8
90 3.543 3 9/16
95 3.74 3 3/4
100 3.937 3 15/16
105 4.134 4 1/8
110 4.331 ---
115 4.527 4 1/2
120 4.724 4 3/4
125 4.921 ---
130 5.118 5 1/8
135 5.315 ---
140 5.512 5 1/2
145 5.709 ---
150 5.905 ---
155 6.102 6 1/8
160 6.299 ---

 

Can you use either a ¼” or 3/8” drive on a 6mm socket?

Yes, you can generally use either a 1/4" or 3/8" drive on a 6mm socket, which will fit both. This is common, particularly for smaller socket sizes. We’ve expounded on what does drive size have to do with socket sizes, but essentially why you would use one over the other has to do with:

  • Torque: While both sizes can handle a 6mm socket, the 3/8" drive generally offers more torque, making it better suited for tighter bolts.
  • Accessibility: In tight spaces, a 1/4" drive with its shorter length might be more convenient.
  • Availability: You might have a 6mm socket in one drive size but not the other. 

In most cases, either a 1/4" or 3/8" drive 6mm socket will work fine. The choice often comes down to personal preference or the specific tools you have on hand. 

Notes:

  • This table covers a range of sizes but might not include all available drive and socket sizes.
  • Not all metric socket sizes have imperial equivalents, and vice versa.
  • Some metric values are close enough to essentially have the same imperial counterpart.
  • Some values are rounded to their nearest thousandth millimeters and ten-thousandth decimal inches.

Important: 

  • Always consult a detailed socket size chart for accurate and precise selection. 

You may want to consider getting the Engineers Black Book (3rd Edition – Metric) for more complete information, specifically:

  • Socket sizing cross-references charts
    • Metric to inch: Socket hex sizes A/F (in mm) and their decimal inch equivalents, nearest alternative socket sizes A/F (in inches) and their difference in values (in mm). Values listed are from 3.5mm to 170mm.
    • Inch to metric: Socket sizes A/F (in inches) and their metric equivalent (in mm), nearest alterative socket size A/F (in mm) and their difference in values (in mm). Values listed are from 3/16” to 7”.

 

More size charts

  • Anchor Bolt Size Chart: Sort through a wide variety of metric anchor bolt types: countersunk head sleeve anchor, drop-in anchor, hex flange nut sleeve anchor, flush head sleeve anchor and stud anchor. Common metric diameters listed.
  • Drill Bit Size Chart: Choose the right bit size to ensure a proper fit for your intended gauge sizing. Metric (SI) and imperial (US decimal / fractional inches) values matched.
  • Fastener Reference Chart: Cross-reference the measurement of your bolt, nut or screw with these comprehensive table of sizes. Metric, Unified Thread Standard and British Thread Standards values matched. There are also simplified illustrations of how to identify metric or imperial fasteners by thread pitch and threads per inch, respectively.
  • Loctite Application Chart: Know which Loctite product to use with various materials and surfaces, from bricks and ceramics to vinyl and wood.
  • Pulley Size Chart: Sort through a wide variety of aluminium and cast-iron pulleys for different belt sections and grooves. For taper locks, pilot bores and bores with keyway. Metric and imperial sizes available.
  • Spanner Size Chart: Find out which spanner size to use for your bolt, nut or screw with a hexagonal head. Metric and imperial (UNC/UNF) sizes matched.
  • Tapping Drill Size Chart for Thread Cutting Taps: Find the appropriate (and nearest alternative) drill size for creating a pilot hole before cutting threads in a workpiece. Common coarse and fine drill sizes listed. Metric and imperial (US decimal / fractional inches) values matched.

 

AIMS' Note on Safe Use of Hand Tools

  • Inspection: Before using any tool, carefully inspect it for cracks, chips, loose handles, worn / mushroomed heads or any other signs of damage. Damaged or defective tools may cause harm! Ensure all guards are in place.
  • Right tool for the job: Make sure you understand the intended purpose of each tool and choose the correct one for your specific job. Don't try to make a screwdriver work as a pry bar or a wrench as a hammer.
  • Safe handling: Carry sharp tools pointed down and away from your body. Never carry tools in your pockets where they can cause injury. When passing a tool to someone, extend the handle first.
  • PPE: Wear safety glasses or goggles to protect your eyes from flying debris. Consider gloves depending on the tool and task to prevent cuts or blisters but without compromising comfort, dexterity and protection. If working with noisy tools, wear ear protection.
  • Maintenance: Keep your tools clean, sharp and properly maintained. Store them in a safe and organised place when not in use.

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