How to Measure Socket Drive Size [An Easy Guide]

Last Updated on June 19, 2022 by TechChecking

Determining the right size socket is essential because without a proper socket drive you cannot fasten or unfasten a nut or bolt. So, knowing how to measure socket drive size can help you find it quickly like an expert. Socket sets are generally sold as a single, box, or pouch containing various replaceable attachments. If you have a whole set of socket drives, you can easily pick the right size if you know the steps on how to measure socket drive. In this article, we will try to focus on how to figure out socket size and how to measure what size socket you need. Let’s get started.


The Systems to Measure Socket Drive Size

We can measure the socket drive size in two systems. The first one is the Imperial system which is measured by inches and the second one is the Metric system which is measured by millimeters. However, the drive socket size is always calculated using an imperial measurement system. The imperial system maintains an international standard level. So, why don’t we know more about the socket drive size measuring systems? Let’s know some information about it.

The Imperial System

The imperial system of units is an imperial system (also known as British Imperial) which was first defined in the British Weights and Measures Act in 1824. It was then gradually developed through time.

The imperial system developed from earlier English units and the imperial units replaced the Winchester Standards that were in effect from 1588 to 1825. However, the imperial system was considered as official use across the British Empire in 1826.

By the late 20th century, most nations were accustomed to using the metric system as their main system of measurement. But imperial units were still used alongside metric units in the United Kingdom and in some other parts of the former empire, notably Canada.

In this modern age, the practice of using an imperial system is mostly seen in the USA. We also see some best automotive tools are manufactured there. And since the USA supplies the tools and equipment all over the world, the imperial system of measurement has increased exponentially.

As we know imperial system measurement is applied to sockets and wrenches in inches and fractions of an inch. The head size of imperial sockets is usually from 5/32 inches to ½ inches. In fact, these ranges of sizes are mostly and commonly used all over the globe. They follow the standard measurement system.

The Metric System

If we simply follow the history we see that the metric system is a measurement system that had been introduced in France in the 1790s. The metrication (adopting the metric system is known as metrication) was started and a new definition was introduced which is called the International System of Units (SI). This name of SI was established under the oversight of an international standards body in the mid-20th century.

However, through a great evolution and time, metric systems have evolved since the 1790s. It is because science and technology were advancing from then. Before the new system SI was innovated, some other metric systems were followed too. They are the MKS system of units and the MKSA systems, which are the direct forerunners of the SI.

In addition, the metric system has seven base units. They are Meter for length, kilogram for mass, Second for time, Ampere for electric current, Kelvin for temperature, Candela for luminous intensity, and Mole for the amount of substance. To be truthful, these can measure any physical quantity.

Moreover, the metric system measurements are applied to sockets, wrenches, and any tools or equipment as millimeters. The head size of the metric sockets ranges from 3 mm to 80 mm.


How to Measure Socket Drive Size

Different types of measuring

We have discussed the systems of how to measure socket drive size and now we are going to elaborate on how to measure a nut for a socket size step by step. If you are quite eager to know about “how do I know what size socket I need”, you need to read the whole paras. We will also show the ways of measuring socket drive size in both imperial and metric systems.

To apply this system, you must require a digital caliper to figure out the socket size quickly. Once you have managed the digital caliper, you are ready to follow the next steps.

Imperial System

Measured in inches digital caliper

Step 1: First, turn on the digital caliper. And then set it to inches (not millimeters) for the measure on imperial systems because the imperial system is followed by inches.

Step 2: At step two, put the nut on a flat surface. A table would be good. Now open the jaws of the digital caliper so that it fits perfectly between the nut and the caliper. Set it properly.

Step 3: Close the caliper jaws perfectly making sure each jaw rests on one flat side of the nut on opposite sides.

Step 4: Now take a closer look to get a clear view and check the caliper display. The reading shows the size of the nut as a decimal. We know that imperial sockets are sized following in fractions of an inch. Since you set the caliper to inches, you need to look at the decimal to fraction. You can check the conversion table below.

Important Note: if you don’t find the value of a fraction in accordance with the size of the measured nuts, you should then find the size of the socket in the metric systems. To know how to measure socket drive size in a metric system, follow the next method.

Metric System

Measured in Millimeters digital caliper

Step 1: Turn on the digital caliper. Set it to millimeters to determine the size of the socket drive.

Step 2: Put the nut on a flat surface like a table. Open the jaws of the caliper and try to set it such as it can perfectly fit with the nut. If you think you have done this part successfully, just close the jaws of the caliper on both the flat side of the nuts.

Step 3: Now take a look at the display of the caliper and check it out. The reading shown on the display is the size of the nut as a decimal. We already know that metric sockets are measured in millimeters. You can convert the millimeter to inches just by checking out the table. However, select the first-millimeter size larger than your caliper reading and this is how you can know the size of your nut and required sockets.


Some Quality Digital Caliper


What Is The Standard Socket Wrench Size?

The standard socket wrench size is very common all over the world. The wrench sizes can be different but to be truthful, there are 3 types of common socket sizes available in the market. They are:

  • 1/4 inches or 0.6 centimeters
  • 3/8 inches or 0.9 centimeters
  • 1/2 inches or 1.3 centimeters

Since these socket wrench sizes are different, you can use these for different purposes.

1/4 inches or 0.6 centimeters – this socket wrench size is comparatively small and is used to do small projects as well.

3/8 inches or 0.9 centimeters – the 3/8 inches socket wrench is medium in size. This is a common and popular size. You can do small to medium type jobs easily and comfortably. A very perfect tool specially used for cars.

1/2 inches or 1.3 centimeters – a ½ inch socket wrench size is the largest of those three sizes. These types of wrenches are good for heavy-duty jobs which are commonly used in industrial work. You can tighten or loosen any nut or bolt up to 10 mm easily and effortlessly.


What are the wrench sizes?

There are a lot of wrench sizes out there. Wrench sizes – I think you are meaning different types of Imperial Combination Wrenches and Metric Combination Wrenches by wrench sizes. If that is the point, let’s see some sizes of wrenches.

  • Imperial Combination Wrenches (1/4, 5/16, 11/32, 3/8, 7/16, 1/2, 9/16, 5/8, 11/16, 3/4, 13/16, 7 / 8, 15/16, 1)
  • Metric Combination Wrenches (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
  • Regular Flare Nut Wrenches (3/8, 7/16, 1/2, 9/16, 5/8, 11/16, 3/4, 7/8)

These are the commonly used wrench sizes. If you have a set of them, you can complete any project at lightning flash speed.


Metric Socket Sizes Chart

Wrench sizes and wrench sizes in order are important to know. The below table will provide enough data and information to get your work done. We hope, this chart will help you a lot. Let’s take a look.

1/4” Drive3/8” Drive1/2” Drive3/4” Drive1” Drive
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

Measurements and Conversions

The table below is a conversion table from fractions to decimals and millimeters and vice-versa. Once you measure either imperial system or metric system, you can take help from here to convert, for example, inches to millimeters. If you want to more about the table, know from here.

[Remember, I inch = 25.4 mm exactly]

Convert fractions to decimals and millimeters and reverse

fractiondecimalmmfractiondecimalmmfractiondecimalmm
1/640.01560.39691 1/641.015625.79692 1/642.015651.1969
1/320.03130.79381 1/321.031326.19382 1/322.031351.5938
3/640.04691.19061 3/641.046926.59062 3/642.046951.9906
1/160.06251.58751 1/161.062526.98752 1/162.062552.3875
5/640.07811.98441 5/641.078127.38442 5/642.078152.7844
3/320.09382.38131 3/321.093827.78132 3/322.093853.1813
7/640.10942.77811 7/641.109428.17812 7/642.109453.5781
1/80.12503.17501 1/81.125028.57502 1/82.125053.9750
9/640.14063.57191 9/641.140628.97192 9/642.140654.3719
5/320.15633.96881 5/321.156329.36882 5/322.156354.7688
11/640.17194.36561 11/641.171929.76562 11/642.171955.1656
3/160.18754.76251 3/161.187530.16252 3/162.187555.5625
13/640.20315.15941 13/641.203130.55942 13/642.203155.9594
7/320.21885.55631 7/321.218830.95632 7/322.218856.3563
15/640.23445.95311 15/641.234431.35312 15/642.234456.7531
1/40.25006.35001 1/41.250031.75002 1/42.250057.1500
17/640.26566.74691 17/641.265632.14692 17/642.265657.5469
9/320.28137.14381 9/321.281332.54382 9/322.281357.9438
19/640.29697.54061 19/641.296932.94062 19/642.296958.3406
5/160.31257.93751 5/161.312533.33752 5/162.312558.7375
21/640.32818.33441 21/641.328133.73442 21/642.328159.1344
11/320.34388.73131 11/321.343834.13132 11/322.343859.5313
23/640.35949.12811 23/641.359434.52812 23/642.359459.9281
3/80.37509.52501 3/81.375034.92502 3/82.375060.3250
25/640.39069.92191 25/641.390635.32192 25/642.390660.7219
13/320.406310.31881 13/321.406335.71882 13/322.406361.1188
27/640.421910.71561 27/641.421936.11562 27/642.421961.5156
7/160.437511.11251 7/161.437536.51252 7/162.437561.9125
29/640.453111.50941 29/641.453136.90942 29/642.453162.3094
15/320.468811.90631 15/321.468837.30632 15/322.468862.7063
31/640.484412.30311 31/641.484437.70312 31/642.484463.1031
1/20.500012.70001 1/21.500038.10002 1/22.500063.5000
33/640.515613.09691 33/641.515638.49692 33/642.515663.8969
17/320.531313.49381 17/321.531338.89382 17/322.531364.2938
35/640.546913.89061 35/641.546939.29062 35/642.546964.6906
9/160.562514.28751 9/161.562539.68752 9/162.562565.0875
37/640.578114.68441 37/641.578140.08442 37/642.578165.4844
19/320.593815.08131 19/321.593840.48132 19/322.593865.8813
39/640.609415.47811 39/641.609440.87812 39/642.609466.2781
5/80.625015.87501 5/81.625041.27502 5/82.625066.6750
41/640.640616.27191 41/641.640641.67192 41/642.640667.0719
21/320.656316.66881 21/321.656342.06882 21/322.656367.4688
43/640.671917.06561 43/641.671942.46562 43/642.671967.8656
11/160.687517.46251 11/161.687542.86252 11/162.687568.2625
45/640.703117.85941 45/641.703143.25942 45/642.703168.6594
23/320.718818.25631 23/321.718843.65632 23/322.718869.0563
47/640.734418.65311 47/641.734444.05312 47/642.734469.4531
3/40.750019.05001 3/41.750044.45002 3/42.750069.8500
49/640.765619.44691 49/641.765644.84692 49/642.765670.2469
25/320.781319.84381 25/321.781345.24382 25/322.781370.6438
51/640.796920.24061 51/641.796945.64062 51/642.796971.0406
13/160.812520.63751 13/161.812546.03752 13/162.812571.4375
53/640.828121.03441 53/641.828146.43442 53/642.828171.8344
27/320.843821.43131 27/321.843846.83132 27/322.843872.2313
55/640.859421.82811 55/641.859447.22812 55/642.859472.6281
7/80.875022.22501 7/81.875047.62502 7/82.875073.0250
57/640.890622.62191 57/641.890648.02192 57/642.890673.4219
29/320.906323.01881 29/321.906348.41882 29/322.906373.8188
59/640.921923.41561 59/641.921948.81562 59/642.921974.2156
15/160.937523.81251 15/161.937549.21252 15/162.937574.6125
61/640.953124.20941 61/641.953149.60942 61/642.953175.0094
31/320.968824.60631 31/321.968850.00632 31/322.968875.4063
63/640.984425.00311 63/641.984450.40312 63/642.984475.8031
1″1.000025.40002″2.000050.80003″3.000076.2000
Source: https://www.hamuniverse.com/antfrac.html

What is the Drive Size of a Socket?

¼ inches, 3/8 inches, and ½ inches are the three common drive sizes of the socket are available. These are the most common sizes that you can find all over the world. They offer a metric socket set.

These are 3 different sizes. The smallest one (¼ inches) is good for small-sized nuts and bolts. The medium one (3/8 inches) is good for fastening and unfastening medium-sized nuts and bolts and the biggest one (½ inches) is used for tightening or loosening for the bigger nuts or bolts.

If you want bigger than a ½” drive size, 1” drive size of a socket is available too. So, you can tell the most common socket sizes are 1/4″, 3/8″, 1/2″, 3/4″, or 1″.


Frequently Asked Questions

1. What are the standard wrench sizes?

Wrench sizes are different to deal with different sizes of nuts or bolts. However, the standard key is in sizes 1/4, 5/16, 11/32, 3/8, 7/16, 1/2, 9/16, 5/8, 11/16, 3/4, 13/16, 7/8, 15/16, and 1.

2. How are the traffic jams in the correct order?

The traffic jams should be in the correct order. They are (1/2 inch) 3/8 inch, 7/16 inch, 1/2 inch, 9/16 inch, 5/8 inch, 11/16 inch, 3/4 inch, 13 / 16 inch, 7/8 inch, 15/16 inch, 1 inch, 11/16 inch, 11/8 inch, 13/16 inch, 11/4 inch.

3. How many contacts are there in a set?

Well, you can see the contacts points in standard sockets. They are used for the best gripping of a nut. The Standard Sockets (5/32, 3/16, 7/32, 1/4, 9/32, 5/16, 11/32, 3/8, 7/16, 1/2 and 9/16 inch) 12 6-point metric sockets (4, 5, 5.5, 6, 7, 8, 9, 10, 11, 12, 13 and 14mm) 10 12pt.

4. What are the standard output sizes in the order?

The standard output sizes in the order are:
Standard Allen keys (5/16, 11/32, 3/8, 7/16, 1/2, 9/16, 5/8, 11/16, 3/4, 13/16)
Metric socket wrenches (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
Deep six-point metric contacts (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
Standard Hex Box (5/32, 3/16, 7/32, 1/4, 5/16, 3/8)

5. What are the dimensions of Allen?

Allen keys are generally measured in fractional size and metric size. The three most common sizes are probably 5/32”, 3/16”, and ¼”. In metric sizes, 4, 5, and 6 mm seem like a lot of stock. Other good SAE sizes are 3/32”, 7/64 “, 1/8”, 9/64” and 7/32”.


Final Words

We hope that the answer is now clear on how to measure socket drive size. We have tried to cover everything you need to know about how to measure socket drive size. Supporting questions are also mentioned there. Questions like how do I know what size socket I need, how to measure what size socket you need, how to figure out socket size, how to measure socket drive, how do you measure socket drive size, etc. are the same question. You can take the same answers that we have discussed here. If you have any queries please let us know. You know how to reach out to us.


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