How To Make An Ethernet Cable (Crossover & Straight-through Method)

This guide explains how to make an Ethernet cable, also called a network cable or patch cable. Making your own cables reduces what you spend on them. You can also cut each Ethernet cable to the exact length you need and choose the wiring that suits the connection you are making. You can follow these instructions for cables you use at home or at work.

First, some information about the Ethernet cables, connectors and wiring. If you are already familiar with this, you can go straight to the guide:

How to make an Ethernet cable ⇓.

Disclosure: Some of the links in this post are affiliate links and if you go through them to make a purchase I will earn a commission. I link to these products because of their quality and not because of the commission I receive. The decision is yours, and whether or not you decide to buy something is completely up to you

What is an Ethernet cable?

An Ethernet cable connects devices in an Ethernet network. These cables carry data between devices over a wired connection. Ethernet is a set of standards for communication between devices such as computers. The cables can also work well for wiring analog PLC inputs and outputs, because their twisted pairs and shielding protect the signals.

You may already use Ethernet in your own local area network. Most personal computers and servers use Ethernet standards. The automation industry uses them too. For example, PROFINET, the sister to PROFIBUS uses Ethernet over twisted pair cabling for communication between PLCs. We will make our Ethernet cable with twisted pair cabling.

Ethernet over twisted pair

Ethernet networks communicate over twisted-pair cables. Inside each cable, the wires twist around each other in pairs along its length. This twisting cancels electrical noise or electromagnetic interference (EMI) from outside.

Noise can interfere with networks, especially when signals travel over longer distances. Twisting the wires in pairs allows differential mode transmission of the signals to cancel the noise.

Twisted-pair Ethernet cables come in several types, including UTP, STP and some others. These types differ from each other and suit different environments. The amount of electrical interference in the environment determines which type of cable to use.

UTP cables

UTP means Unshielded Twisted Pair. These cables have no shield around the individual wires or pairs. They sometimes serve as patch cables in homes or offices.

They are never used in industrial or noisy environments because noise can affect their signals. Twisting the wires still leaves the signals vulnerable where there is a lot of electrical interference.

STP cables

STP means Shielded Twisted Pair. The name commonly covers all shielded twisted pair cables. Several types are available, with different shielding arrangements. Each uses a shield or foil to protect its signals from noise.

Twisted pair cables can use foil as well as a shield. FTP (Foiled Twisted Pair) has a layer of metal foil around all the wires, around every pair or around both.

You can buy each of these types of twisted pair cables with different specifications, using stranded or solid-core wires. Stranded wires flex because each consists of many smaller wires. This construction makes the cable flexible. Solid-core wires have a solid conductor instead, so they do not flex as easily. They are usually used in fixed installations.

Twisted pair cable is available in different wire thicknesses, usually 22 and 24 AWG. For longer Ethernet cables, use twisted-pair cable with the highest AWG number. Resistance increases with cable length, while thicker wires lower the resistance. Higher resistance means a slower network connection.

Ethernet cable categories – Cat cables

Ethernet cable comes in categories defined by the available bandwidth, with each category used for different purposes. Category 3, or cat3, cable is used for telephone connections, for example. The twisted pair cable categories are defined in ISO 11801.

This guide covers Ethernet cables with RJ45 connectors at each end, which you can make yourself. You will need one of the cable categories below.

Cat5 Ethernet cable

Used for short distances in LAN (100Base-Tx).

Category 5, or cat5 Ethernet cable, normally suits environments protected from noise. It supports up to 100 Mbit/s. Since cat3 and cat4 are not used for Ethernet cables, cat5 is the slowest Ethernet cable you can make.

Cat5e Ethernet cable

Getting a little better with faster transmission speed (1000Base-T).

This category extends category 5. Its specifications are almost the same as cat5, apart from some limits such as the return loss. Those differences allow cat5e cables to carry data faster than cat5 cables.

Cat6 Ethernet cable

Now, we are there! Suitable for up to 10GBASE-T.

Providing up to 10 Gbit/s, category 6 cables give the fastest connection. Although they are not fiber, cat6 cables deliver the highest Ethernet speed you can make yourself.

For a comparison, see this comparison of the cable categories 3 to 7, used for Ethernet. Read more about CAT 6 cables here.

RJ45 connector

Twisted-pair Ethernet cables use RJ45 connectors. RJ45 is their common name; another is 8 Position 8 Contact, or 8P8C.

An RJ45 connector has 8 pins, one for each wire in a typical Ethernet cable with 4 wire pairs. The RJ45 connector connects in only one orientation. A small part on top ensures it fits only one way. Here is the RJ45 pinout:

Check the position of every pin # before making your Ethernet cable. You will use a crimp tool to connect the cable to the RJ45 connector.

Crimping makes the connection permanent, so you cannot go back and rearrange the wires afterward. Check that the wires are in their correct positions first. If they are not, you will need to start again with another connector. Keep some spare connectors for practice.

RJ45 UTP connector

One option for making Ethernet cables is an RJ45 UTP connector. As with the cables, UTP means shielded twisted pair. The UTP connector has no shield and is made entirely of plastic.

Without a shield to deal with, the RJ45 UTP connector is the simplest to use. It works with both shielded and shielded twisted pair cables.

You can buy 100 of these UTP connectors at a low price on Amazon.

Each RJ45 connector pin has a sharp edge that cuts into the wire to make an electrical connection.

RJ45 STP connector

The other option is an RJ45 STP connector. Like the UTP connector, it has a plastic body. A metal shield, or housing, surrounds the STP connector.

Packs of 100 are available on Amazon.

RJ45 crimp tool

To connect the wires electrically, insert them into the RJ45 connector and press down its pins with an RJ45 crimp tool. The tool also presses the connector opening around the cable to secure it.

A good-quality RJ45 crimp tool is available at a low price here on Amazon. You can also read reviews on the best RJ45 crimper on the market.

Ethernet Cable Wiring

Ethernet cables can use several wiring arrangements. Two common options follow the T568A and B standards. These standards keep the signals in wire pairs so they benefit from the noise-canceling effect of the twists. Following these standards also helps when you want to make a crossover Ethernet cable. As we will see below, their wiring arrangements make the crossover easy to create.

T568A Wiring

T568A is the first wiring standard, often shortened to A. It assigns each wire color to a particular pin number.

Here is the T568A wiring arrangement for an RJ45 connector:

Source: Wikipedia

T568B Wiring

The other standard, T568B, swaps the orange and green pairs used in the A standard. The T568B wiring arrangement is shown below:

Source: Wikipedia

Straight-through Ethernet cable

You can make two types of Ethernet cable. The simplest is a straight-through cable, wired the same way at both ends. Each wire connects a pin number at one end to the same pin number at the other.

For a straight-through Ethernet cable, choose either T568A or T568B and use that standard at both ends.

When extending an existing network, check its straight-through cable wiring standard and continue using it. Keep the choice consistent across all your cables.

Ethernet crossover cable

The second type is a crossover Ethernet cable. It swaps the wires that send and receive data.

Each pin # in a computer’s RJ45 connector has a defined function, for example. Two pins send data and two receive it. Connecting two computers therefore needs an Ethernet crossover cable.

Swap the two sending and receiving wires at one end to make the correct connections. This connects the sending pins on one computer to the receiving pins on the other.

Ethernet crossover cables are used when connecting similar devices.

On similar devices, the sending and receiving functions use the same pin numbers.

Most Ethernet crossover cables use T568A at one end and T568B at the other. This gives us another reason to use these standards.

The A and B standards differ by two swapped wire pairs: the pairs that send and receive data.

The diagram above shows the crossover cable wiring, with the A standard at one end and B at the other.

How to make an Ethernet cable

Some items are too complex or dangerous to make yourself, such as a whole house surge protector or electrical circuit tracer. An Ethernet cable is simple enough to make yourself.

Making one requires neither an electrical engineering degree nor an electrical apprenticeship ; the process is simpler than it looks.

The video tutorials and step by step instructions below show you how to make an Ethernet cable, so you can see what the process involves.

The first video shows the process using RJ45 UTP connectors:

The second video uses shielded RJ45 connectors, also called STP connectors.

Ethernet cable tutorial – Step by step

1. Strip the cable to expose at least 2 cm, or about an inch, of wire. Use a gwood wire stripper or knife. Take care as you strip the cable: you must not cut the insulation around the individual wires. When you are learning, it can help to strip a little more cable so the wires are longer. That leaves more room to work in the next step.
2. Use your fingers or nails to untwist and straighten every wire.
3. Arrange the wires in the correct color order for A or B. Hold the cable between your thumb and index finger with only the wires visible, then place them in the required order.
4. Keep holding the cable so the wires stay in order, then trim them to 13 mm.
5. Hold the RJ45 connector in your other hand, orienting it so each pin number lines up with the correct wire. Check the RJ45 connector’s orientation before continuing.
6. Slowly insert the wires into the RJ45 connector, guiding each into its own track toward the pin. This can take a few tries, and you might need to repeat steps 2 and 3.
7. Check that every wire reaches the correct pin number (read more about RJ45 pinouts)
8. Push the cable into the RJ45 connector until you can see every wire at the connector’s front.
9. Put the RJ45 connector into the RJ45 plug on the crimp tool. Check that it is seated, then press the tool all the way down.
10. Finally, inspect the wires to check their connections and order. Give the connector a slight pull to confirm that it holds the cable securely.

The first few attempts can be tricky, especially with thick wires. Practice makes the work easier, and you may come to enjoy making Ethernet cables.

If you enjoyed this guide or have tips from making your own Ethernet cables, leave a comment below or write to me.