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 at home. The standard measurement for wire and steel is in gauge but most people rarely understand that unit thus the need for conversion to mm.

The measurement varies from one item to another, for instance one standard used for wires is different from that of steel. The thickness varies from one metal to another, 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 to help you!

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


Wire gauge shows the diameter from which you can easily get its current carrying capacity. From the size you can easily get to know the physical appearance of a wire, current carrying capacity, electrical resistance and weight.

With the standards that are being used, it is so much 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 where it was used to try and indicate the size of a metal. At the beginning, the unit was not uniformly defined but one easily got to know the wire to be used for a specific purpose.

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 means that it has been drawn one. Gauge 18 also means that it has been drawn 18 times.

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

Types of wire systems

there are two main types standards which are

  • empirical
  • geometric


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

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


First started in Great 1855 and is a progression of 39 steps where a 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 also known as British imperial standard is the standard way of wire measurement in the UK. It was adopted in 1883 as a replacement to its preceding unit known as the Birmingham Wire Gauge.

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

American (AWG)

The standard, also known as Brown and Sharpe Wire Gauge, used in measurement in 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.

Just like in other systems, when the number is large the diameter is usually small because 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 in relation to 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 standard was established by the International Electrotechnical Commission on conductors of insulated cables.

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

Importance of choosing the right one

If properly checked wire gauge helps out in a lot of things, some which are common knowledge with others being unknown to most people. Getting to understand the diameter gives you the ability to ably 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 or 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 that are usually caused by wires that melt when excessive current passes through them. With the right cable, you will have your house and property safe from possible electrical fires.
  3. Making the wrong choicecan damage your electronic appliances in the event 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 without much struggle which is important for long distance and high voltage electricity transmission.
  6. With the gauge you can get the weight per unit length which will subsequently help you calculate the whole roll if needed to.

Choosing electrical components

Successfully choosing the right part is one of the hardest tasks for any person willing to make some repairs while at home. A wrong choice could leave your house in flames or blow 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. Whether at home or in work places, before getting a new wire first get to know the amps it is required to carry. 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 and from there they will advise on what you should be buying. Getting the right cable as earlier stated 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 the selection of the right choice for your intended use. If the electricity is to be transferred through long distances you need to account for energy losses through heat.

To account for the loss, you can use a lower number which will accommodate higher current transfer. When you allow for higher current transfer, you get the desired electricity despite the heat loss.


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

For indication

Insulation is also used as an indicator and differentiates the various types of cables in use. For instance, by throwing a glance you can notice a hot wire if you see a black or red coating around them. Green coated ones are for grounding but in some cases, you might find people who rarely follow the codes and the green contains the live wires. Before dealing with these products, first 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 it. Some countries have made it mandatory for the information to be well displayed for all interested parties to view. A well-marked pair of wire helps even those who are clueless on what to purchase since they can buy the right one by only knowing the amperes required.

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.

4- gauge candle about 60 amps.

It is advisable to always pick one with 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. In the chart below the units are represented in inches, millimeters and square millimeters.

wire gauge

Credit: Useful Magnets

Electrical Safety Tips

When dealing with electricity there is a need to observe safety tips that ensure when you are using it you minimize your danger of getting hurt. 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 what their functions are 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, when very thin the metal is known as foil while 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 measurements thus requires a chart for easier conversion. The corresponding numbers range between 3-30 and is 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 similar thickness. To understand it properly and to make sure you get the right product, you need a conversion chart to help you change it to millimeters or inches.

How it started

It shares the same origin with the British system where it was 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 in use till today.

How to read

Reading a steel chart requires little time to understand the metal thickness it stands for. When it 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 millimeter to inches is as easy as using your phone calculator by a value that has been calculated and found to get the corresponding value. 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 that includes the corresponding measurements for other metals of corresponding gauge as well.

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