RJ45 Wiring Diagram: T568A/T568B Color Code, Pinout and Crimping



Need the correct RJ45 wiring order? The short answer is simple: for most Ethernet patch cables, use T568B on both ends. If your building, panel, or wall jack already uses T568A, use T568A on both ends instead. The important rule is consistency: both ends of a straight-through Ethernet cable should use the same wiring standard.

This guide explains the RJ45 pinout, T568A and T568B color codes, how to crimp an RJ45 connector, how to test the cable, and how to choose the right RJ45 connector for Cat5e, Cat6, Cat6a, shielded, and unshielded Ethernet cables.

If you are selecting RJ45 connectors for a product, network device, industrial controller, or PCB assembly, the wiring standard is only one part of the decision. Connector type, cable diameter, conductor style, shielding, PoE requirements, and mechanical durability all affect final performance.

Quick Answer: RJ45 Wiring Color Code

For most modern Ethernet patch cables, use T568B:

Pin	T568B Wire Color
1	White/Orange
2	Orange
3	White/Green
4	Blue
5	White/Blue
6	Green
7	White/Brown
8	Brown

For T568A:

Pin	T568A Wire Color
1	White/Green
2	Green
3	White/Orange
4	Blue
5	White/Blue
6	Orange
7	White/Brown
8	Brown

T568A and T568B provide the same Ethernet performance. The difference is the position of the orange and green pairs.

What Is an RJ45 Connector?

An RJ45 connector is the common modular plug used for Ethernet network cables. In everyday use, people call the Ethernet plug an RJ45 connector, although the technical connector format is often referred to as 8P8C, meaning eight positions and eight contacts.

RJ45 connectors are used in:

• Ethernet patch cables
• Routers and switches
• Computers and network cards
• IP cameras
• VoIP phones
• Industrial Ethernet devices
• Patch panels and keystone jacks
• PCB mount Ethernet ports

The connector may look simple, but a small wiring mistake can cause slow speed, unstable connection, no link, or failed PoE power delivery.

RJ45 Pin Numbering: How to Identify Pin 1

Before wiring an RJ45 plug, make sure you are looking at the connector the correct way.

Hold the RJ45 plug with:

• The metal contacts facing you.
• The locking clip facing down.
• The cable entry pointing away from you.

From this view, pin 1 is on the left and pin 8 is on the right.

This orientation matters because many wiring mistakes happen when the connector is viewed backward. Keystone jacks and PCB mount RJ45 connectors may show the same pinout differently, so always check the product drawing or wiring label before termination.

T568A Wiring Standard

T568A is one of the two recognized Ethernet wiring standards. It places the green pair on pins 1 and 2, while the orange pair moves to pins 3 and 6.

Scroll horizontally to view the full table.

Pin	Pair	T568A Wire Color	10/100 Ethernet Function
1	Pair 3	White/Green	TX+
2	Pair 3	Green	TX-
3	Pair 2	White/Orange	RX+
4	Pair 1	Blue	Not used in 10/100, used in Gigabit/PoE
5	Pair 1	White/Blue	Not used in 10/100, used in Gigabit/PoE
6	Pair 2	Orange	RX-
7	Pair 4	White/Brown	Not used in 10/100, used in Gigabit/PoE
8	Pair 4	Brown	Not used in 10/100, used in Gigabit/PoE

Use T568A when:

• Existing cabling is already wired to T568A.
• The installation specification requires T568A.
• You are matching a patch panel or keystone jack labeled for T568A.

T568B Wiring Standard

T568B is the most common wiring standard in many commercial and residential Ethernet installations. It places the orange pair on pins 1 and 2, while the green pair moves to pins 3 and 6.

Scroll horizontally to view the full table.

Pin	Pair	T568B Wire Color	10/100 Ethernet Function
1	Pair 2	White/Orange	TX+
2	Pair 2	Orange	TX-
3	Pair 3	White/Green	RX+
4	Pair 1	Blue	Not used in 10/100, used in Gigabit/PoE
5	Pair 1	White/Blue	Not used in 10/100, used in Gigabit/PoE
6	Pair 3	Green	RX-
7	Pair 4	White/Brown	Not used in 10/100, used in Gigabit/PoE
8	Pair 4	Brown	Not used in 10/100, used in Gigabit/PoE

Use T568B when:

• You are making a standard Ethernet patch cable.
• The existing network uses T568B.
• The patch panel or wall jack is labeled for T568B.
• You want to match the most common commercial wiring convention.

T568A vs T568B: Which One Should You Use?

For normal Ethernet performance, T568A and T568B are equivalent. A cable wired T568A on both ends and a cable wired T568B on both ends can both support Ethernet when the cable category and connector quality are correct.

The practical rule is:

• Use T568B for most new patch cables.
• Use T568A if the existing system already uses T568A.
• Do not randomly mix standards in the same structured cabling system.

The key is to keep both ends of the same cable consistent unless you intentionally need a crossover cable.

Straight-Through vs Crossover Ethernet Cables

Straight-through cable

A straight-through cable uses the same wiring standard on both ends:

• T568A to T568A
• T568B to T568B

Use straight-through cables for:

• Computer to switch
• Router to switch
• Patch panel to switch
• IP camera to PoE switch
• Most modern Ethernet connections

Crossover cable

A crossover cable uses T568A on one end and T568B on the other end.

Historically, crossover cables were used for device-to-device connections, such as computer to computer or switch to switch. Many modern devices support Auto MDI-X, which can automatically handle transmit and receive pair matching, so crossover cables are less common than they used to be.

Still, if you are troubleshooting older equipment, industrial devices, or legacy networking hardware, knowing the difference can save time.

How to Crimp an RJ45 Connector Step by Step

Use the correct connector for your cable type before you start. A Cat6 cable may not fit well into a connector designed only for smaller Cat5e cable. Solid and stranded conductors may also require different plug designs.

Tools and materials

You will need:

• Ethernet cable, such as Cat5e, Cat6, or Cat6a
• RJ45 connectors matched to the cable
• Cable stripper
• RJ45 crimping tool
• Flush cutter or scissors
• Cable tester
• Optional strain relief boots

Step 1: Strip the cable jacket

Remove about 25 to 30 mm of the outer jacket. Do not cut into the insulation of the inner conductors. If the copper conductor is nicked, cut off the damaged section and start again.

Step 2: Untwist and arrange the pairs

Untwist only as much wire as needed. Excessive untwisting can reduce signal performance, especially for Cat6 and Cat6a cables.

Arrange the wires in the correct order for T568A or T568B.

For T568B:

1. White/Orange
2. Orange
3. White/Green
4. Blue
5. White/Blue
6. Green
7. White/Brown
8. Brown

Step 3: Flatten and trim the wires

Hold the wires flat and parallel. Trim the ends evenly so every conductor reaches the front of the RJ45 plug.

If one wire is shorter than the others, it may not contact the metal blade inside the plug.

Step 4: Insert the wires into the RJ45 plug

Push the wires fully into the plug. Check that:

• The wire order is still correct.
• Every conductor reaches the front of the connector.
• The cable jacket enters the strain relief area of the plug.
• No wire has crossed over another wire.

Step 5: Crimp the connector

Insert the plug into the crimping tool and press firmly. The metal contacts should pierce the conductor insulation, and the strain relief should clamp the cable jacket.

Do not crimp halfway. A weak crimp can create intermittent connection problems.

Step 6: Test the cable

Use a cable tester before installing the cable. A visual inspection alone is not enough. A tester can detect open wires, shorts, reversed pairs, and split pairs.

RJ45 Cable Testing: Common Results and What They Mean

Scroll horizontally to view the full table.

Tester Result	Likely Problem	What to Check
Open wire	One conductor is not connected	Check if the wire reached the front of the plug
Short	Two conductors are touching	Check for damaged insulation or poor trimming
Reversed pair	Wires are in the wrong order	Compare both ends against the T568A/T568B table
Split pair	Pin order looks close but pair grouping is wrong	Rewire the connector using the correct color pairs
No continuity	Bad crimp or broken conductor	Re-crimp or replace the cable section
Works at 100 Mbps but not Gigabit	One or more pairs are faulty	Check all eight conductors, not only pins 1, 2, 3, and 6

For Gigabit Ethernet, all four pairs are used. A cable that appears to work at lower speed can still fail at Gigabit speed if pins 4, 5, 7, or 8 are not terminated correctly.

How to Choose the Right RJ45 Connector

The best RJ45 connector depends on the cable and application. Do not choose only by price or appearance.

Cat5e vs Cat6 vs Cat6a

Cable Type	Connector Consideration
Cat5e	Standard RJ45 plugs usually fit, but check conductor type
Cat6	Often needs larger cable entry and better pair separation
Cat6a	May require shielded or high-performance connectors with larger diameter support

Solid vs stranded conductors

Solid conductors are common in permanent building cable. Stranded conductors are common in flexible patch cables.

Some RJ45 plugs are designed for solid wire, some for stranded wire, and some support both. Using the wrong type can cause weak contact or early failure.

Shielded vs unshielded connectors

Use shielded RJ45 connectors when:

• The cable is shielded.
• The installation has high electromagnetic interference.
• The cable is used in industrial equipment.
• The application involves long runs near motors, drives, or power cables.

Use unshielded RJ45 connectors when:

• The cable is unshielded.
• The installation is a normal office or home network.
• Shield grounding is not part of the system design.

Pass-through vs standard RJ45 plugs

Pass-through RJ45 plugs allow the wires to pass through the front of the connector before crimping. This can make wire order easier to verify.

Standard RJ45 plugs require careful trimming before insertion. They are widely used and reliable when crimped correctly.

Choose based on installer preference, tool compatibility, and project requirements.

PCB mount RJ45 connectors

For network devices, controllers, gateways, routers, and industrial equipment, the RJ45 connector may be mounted directly to a PCB. In this case, selection factors include:

• Shielding
• Integrated magnetics
• LED options
• PoE compatibility
• Contact plating
• Reflow or through-hole process
• Mechanical retention
• Operating temperature

If your product needs an RJ45 connector for a PCB or device enclosure, soulin can help match the connector type to your cable, board layout, and application requirements.

Common RJ45 Wiring Mistakes

Mistake 1: Viewing the connector backward

Pin 1 changes position when you flip the connector around. Always check the orientation before arranging wires.

Mistake 2: Mixing T568A and T568B by accident

Using A on one end and B on the other creates a crossover cable. That may work with some modern devices, but it is not the right choice for most patch cables.

Mistake 3: Untwisting too much wire

Too much untwisted wire can reduce signal quality. Keep the twist as close to the connector as practical.

Mistake 4: Using the wrong connector for the cable

A plug that does not match the cable diameter, conductor style, or category can create poor contact or unstable performance.

Mistake 5: Not testing the finished cable

Always test the cable after crimping. A cable can look correct and still fail under real network conditions.

RJ45 Wiring for PoE Applications

Power over Ethernet, or PoE, sends power and data through the Ethernet cable. This is common for:

• IP cameras
• Wireless access points
• VoIP phones
• Access control systems
• Industrial sensors

For PoE applications, connector quality matters. Poor contact can create heat, voltage drop, intermittent resets, or unreliable device operation.

When selecting RJ45 connectors for PoE, check:

• Current rating
• Contact plating
• Cable category
• Shielding requirements
• Mating durability
• Operating temperature
• Compliance requirements for the final device

RJ45 Connector Selection Checklist

Before ordering RJ45 connectors, confirm:

• Cable category: Cat5e, Cat6, Cat6a, or higher.
• Cable diameter.
• Conductor type: solid or stranded.
• Shielding: UTP, FTP, STP, or S/FTP.
• Plug type: standard, pass-through, field-terminable, keystone, or PCB mount.
• Application: office network, industrial Ethernet, PoE, equipment panel, or PCB assembly.
• Required durability and operating temperature.
• Packaging and production volume.

If you are unsure which RJ45 connector fits your application, send us your cable specification, drawing, or product requirements. Our team can recommend a suitable connector option.

FAQ

Conclusion

RJ45 wiring is straightforward once you understand pin numbering and the difference between T568A and T568B. For most patch cables, T568B on both ends is the practical default. For existing systems, match the standard already used by the patch panel, wall jack, or project specification.

Correct wiring is only part of a reliable Ethernet connection. The connector also needs to match the cable category, conductor type, shielding, and application environment. For products, industrial equipment, PoE devices, and PCB assemblies, choosing the right RJ45 connector helps prevent signal loss, unstable links, and long-term reliability problems.

Need RJ45 connectors for cable assembly or PCB production? Send soulin your cable category, shielding requirement, drawing, or product application for a matching product quotation.