Wire & steel gauge chart to mm: 00, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 

Getting to know the size of your cable or steel goes a long way in ensuring that you purchase the right items for use. The standard measurement for wire and steel is in gauge. Most people rarely understand that unit, thus the conversion to mm.

The measurement varies from one item to another. The standard used for wires is different from steel. The thickness varies from one metal to another, making it confusing. Steel and aluminum standards vary in thickness. Whether you’re trying to convert thicknesses for one thing or something like SAE, it’s always convenient to have a chart available!

While dealing with wires and cables, knowing the difference between the two is good. A wire is an electrical conductor, while a cable is a group of conductors enclosed in a cover.

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Wire gauge shows the diameter from which you can easily get its current carrying capacity. You can easily get to know the physical appearance of a wire. It’ll provide you with information on the electrical resistance and the weight of the size.

With the standards being used, it is easier to determine the cable to use for a specific purpose. Using a cable to transmit more electricity than the recommended amount can damage the part. At times it can lead to your house burning if installed at home.


The use of wire gauge as a unit of measurement started in Great Britain earlier than 1750. It was used to try and indicate the size of the metal. In the beginning, the unit was not uniformly defined. Still, one easily got to know the wire to be used for a specific purpose.

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It can be defined as the number of times a wire has been drawn from the original size. It starts from zero, with zero being the original size and one having drawn one. Gauge 18 also means that it has been drawn 18 times.

Drawing is the process of passing a wire through a die to reduce its diameter to one that can be easily manipulated for a specific purpose. Ones for transmitting industrial electricity will differ in size from the one used for domestic lighting. The difference in needs for different purposes led to the development of cables with different thicknesses according to purpose.

Types of wire systems

there are two main types of standards, which are:

  • empirical
  • geometric


The oldest wire measurement method was used as early as the early 18th century. It is a basic method with no complex calculations involved but is based on the number of times a wire has been drawn. The system starts with the original rod as 0000. With each subsequent draw, we get a higher number. If drawn 18 times, we get gauge 18.

Despite being used since the 18th century, this system is still in use today. It is preferred for its simplicity, unlike the other methods where you have to involve complex computations to get to a value.


It first started in Great Britain in 1855 and is a progression of 39 steps where the diameter is multiplied by 0.890526 to get the next. It was created to bring exactness in the measurements for accuracy when dealing with the wires. It is mostly used in North America.

Imperial standard (SWG)

The imperial standard is also known as the British imperial standard. It is the standard way of wire measurement in the UK. It was adopted in 1883 to replace its preceding unit known as the Birmingham Wire Gauge.

The units in this system are mainly represented in inches and fractions of inches. You can easily convert the units to the metric system with the improving technology.

American (AWG)

The standard is also known as Brown and Sharpe Wire Gauge. It is used to measure the United States and North America. It mainly uses the metric system to indicate the diameter. This system was first used in 1857 to introduce uniformity in the industry by the different manufacturers.

Like other systems, the diameter is usually small when the number is large. The larger the number, the more times it has been drawn. It is also important to note that the AWG or SWG numbers do not factor in the size of the insulation.

AWG is a 39-step logarithmic sequence with 0000 AWG defined as 0.46 inches in diameter and 36 AWG as 0.005 inches in diameter. To get the other sizes, you need to derive them mathematically in between the sizes.

Poorer conductors like aluminum are given correction factors about the copper AWG size to get their current carrying capacity.

IEC 60228

IEC 60228 is the standard used in most parts of the world to represent the various sizes of the wire. The International Electrotechnical Commission established the standard on conductors of insulated cables.

IEC uses the metric system for the representation of the sizes it holds. It is good to note that AWG, SWG, and IEC are different systems. Without a converter, one cannot represent the other. Systems like the SWG round up their figures. The units they give may not be accurate if considered in another mode of representation.

Importance of choosing the right one

If properly checked, the wire gauge helps out in many things. Some of which are common knowledge, others are unknown to most people. Understanding the diameter allows you to purchase the right cable without fear.

Some of the advantages of knowing the size include:

  1. You get to know the current carrying capacity of the cable. You’ll know the right cable to purchase even before you go to the electronics shop to acquire one.
  2. With the right cable, you prevent electrical fires caused by wires that melt when excessive current passes through them. With the right cable, your house and property will be safe from possible electrical fires.
  3. Making the wrong choice can damage your electronic appliances if only a little current gets to the amplifier damaging it.
  4. Incorrect size might lead to poor sound quality from the sound system if it does get the right voltage in the amplifier. Low voltage might not be even enough for sound transmission to the speakers.
  5. Once you get to know the system, you can comfortably get the resistance of the wire. It won’t be a struggle. Knowing the right cable is especially important for long-distance and high voltage electricity transmission.
  6. With the gauge, you can get the weight per unit length, which will help you calculate the whole roll if needed.

Choosing electrical components

Successfully choosing the right part is one of the hardest tasks for anyone willing to make some repairs while at home. A wrong choice could leave your house in flames or blow up some of your appliances.


When choosing the right component, the first option should be considering the required gauge. Getting the right one will help you acquire one that will carry the amount of electricity required without straining. Before getting a new wire, first, get to know the amps you must carry at home or in the workplace. By doing this, you reduce the possibility of straining it.

If you don’t know the current it can carry, ask the store operators to advise on the right one to buy. They might need to know what you intend to power. From there, they will advise on what you should be buying. Getting the right cable is the first step to keeping your devices safe from electrical damage.


The distance you intend to take the electricity also plays a big role in selecting the right choice for your intended use. If the electricity is to be transferred long distances, you need to account for energy loss through heat.

You can use a lower number to accommodate a higher current transfer to account for the loss. You get the desired electricity despite the heat loss when you allow for the higher current transfer.


Before purchase, ensure that it is well insulated. Insulation serves several purposes, with the main one being keeping people from the danger of electrocution. With good insulation, even high voltage lines will not harm you.

For indication

Insulation is also an indicator and differentiates the various types of cables used. For instance, you can notice a hot wire by throwing a glance if you see a black or red coating around them. Green-coated ones are for grounding. You might find people who rarely follow the codes, and the green contains the live wires. Before dealing with these products, confirm whether it has been used for grounding.

Government regulations

In some countries, all wires and cables are designed in a way that it comes displaying the cable it holds inside them. Some countries have made it mandatory for the information to be well displayed for all interested parties to view. A well-marked pair of wires helps even those clueless on what to purchase. They can buy the right one by only knowing the required amperes.

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Some of the gauge measurement against amps usage includes;

18 gauge is for low voltage lighting with a maximum wattage of about 10 amps.

16 gauge can be used on cords that conduct up to 13 amps.

10 gauge can be used on larger appliances like cloth dryers & electric water heaters.

red extension cord

4 gauge can handle about 60 amps.

It is advisable always to pick one with a thicker diameter to be safe whenever in doubt on which one to pick.

Wire gauge to mm chart

With a conversion chart, you can easily move from one unit of measurement to another without much struggle. The units are represented in inches & millimeters in the chart below.

wire gauge

Credit: Useful Magnets

Electrical Safety Tips

When dealing with electricity, there is a need to observe safety tips. They ensure you minimize your danger of getting hurt when you are using it. The tips include:

a.) When working on electric cables, ensure that you have switched off the mains.

b.) Use the right cable for electric conduction to avoid damage to your property.

c.) Use the appropriate colors to represent the cables and their functions while in use.

d.) Install outlet covers to protect your kids from electrocution when not in use.

e.) Have multiple outlets to reduce the chances of overloading one.


Steel gauge is used in characterizing metal thickness in flat sheets. For instance, the metal is a foil when very thin. Thicker metals are known as plates. Just like in AWG, the system is based on non-linear measurements and represented in fractions of inches.

The steel gauge is not easy to read and convert to standard units of measurement. It requires a chart for easier conversion. The corresponding numbers range from 3 to 30 and are based on the weight of the metal sheet.

Based on the weight of the metal sheet, two different metals may vary in gauge despite having a similar thickness. To understand it properly and to make sure you get the right product, you need a conversion chart. It will help you change it to millimeters or inches.

How it started

It shares the same origin with the British system, based on the number of times it was drawn. They share similar characteristics, such as representation in fractions of inches. It has survived several generations, remaining the main method used until today.

How to read a steel chart

Reading a steel chart requires little time to understand the metal thickness it stands for. When one should consider the following feature:

  1. The distances between one gauge and another are not equidistant.
  2. The readings vary with the type of metal in use. Always consider the decimals to get accurate readings of the metal.

Conversion of mm to inches

Changing from millimeters to inches is as easy as using your phone calculator. Some phones also have an inbuilt inverter that converts several measurement units to another.

The conversion multiplier is 0.023937007874. Once you multiply your value in millimeters by this, you get your answer in inches.

There are also online converters that you can use to find the value in inches and vice versa.

Steel gauge to millimeter chart

The image below shows a steel gauge conversion chart. It includes the corresponding measurements for other metals of the corresponding gauge.

Do you want to buy more wires but don’t know where to start to make the best choice?

Fortunately for you, we can come to your aid.

We will give you all the steps you need to follow in choosing the best type of electric cable to suit your needs.