RJ45 pinout wiring diagram

The RJ45 pinout is one of the most searched topics in networking, with "RJ45 pinout" receiving approximately 8,100 Google searches per month. Whether you are crimping a patch cable, wiring a wall plate, or designing a PCB with an ICM RJ45 connector, understanding the correct pin assignment is essential. This guide covers the two RJ45 wiring standards, T568A and T568B, their pin assignments, when to use each, and common wiring mistakes to avoid. We also cover the pinout for different Ethernet speeds (10/100Base-T vs 1000Base-T) and PoE wiring. T568A vs T568B: The Two Wiring Standards There are two recognized wiring standards for RJ45 connectors, defined by TIA/EIA-568: T568A: Defined by TIA/EIA-568-A (1991). The older standard, still required by some government and military contracts. In T568A, Pair 1 (blue) is on pins 4-5, Pair 2 (orange) is on pins 3-6, Pair 3 (green) is on pins 1-2, and Pair 4 (brown) is on pins 7-8. T568B: Defined by TIA/EIA-568-B (2001). The more common standard, used in most commercial and residential installations. In T568B, Pair 1 (blue) is on pins 4-5, Pair 2 (green) is on pins 3-6, Pair 3 (orange) is on pins 1-2, and Pair 4 (brown) is on pins 7-8. The only difference from T568A is that the orange and green pairs are swapped. 💡 Key Point:T568A and T568B are functionally identical. The only difference is the color assignment of the orange and green pairs. Both standards deliver the same performance. Choose one standard and use it consistently throughout your installation. Complete RJ45 Pinout Tables T568B Pinout (Most Common) Pin Wire Color Pair 10/100Base-T 1000Base-T PoE (802.3af/at) 1 White/Orange 2 TX+ BI_DA+ Mode A: Positive (V+) 2 Orange 2 TX- BI_DA- Mode A: Positive (V+) 3 White/Green 3 RX+ BI_DB+ Mode A: Negative (V-) 4 Blue 1 Not used BI_DC+ Mode B: Positive (V+) 5 White/Blue 1 Not used BI_DC- Mode B: Positive (V+) 6 Green 3 RX- BI_DB- Mode A: Negative (V-) 7 White/Brown 4 Not used BI_DD+ Mode B: Negative (V-) 8 Brown 4 Not used BI_DD- Mode B: Negative (V-) T568A Pinout Pin Wire Color Pair 10/100Base-T 1000Base-T 1 White/Green 3 TX+ BI_DA+ 2 Green 3 TX- BI_DA- 3 White/Orange 2 RX+ BI_DB+ 4 Blue 1 Not used BI_DC+ 5 White/Blue 1 Not used BI_DC- 6 Orange 2 RX- BI_DB- 7 White/Brown 4 Not used BI_DD+ 8 Brown 4 Not used BI_DD- Side-by-Side Comparison Pin T568A Color T568B Color Same? 1 White/Green White/Orange No (swapped) 2 Green Orange No (swapped) 3 White/Orange White/Green No (swapped) 4 Blue Blue Yes 5 White/Blue White/Blue Yes 6 Orange Green No (swapped) 7 White/Brown White/Brown Yes 8 Brown Brown Yes Which Standard Should You Use? General Rule Use T568B for commercial and residential installations (it is the more common standard in the US and most of the world). Use T568A if required by contract specifications (some government and military projects mandate T568A). The critical rule is consistency: both ends of a straight-through cable must use the same standard. Straight-Through vs Crossover Cables Straight-through cable: Both ends use the same standard (e.g., T568B on both ends). Used for connecting different device types (PC to switch, switch to router). This is the standard patch cable used in 99% of installations. Crossover cable: One end uses T568A, the other uses T568B. Used for connecting same-type devices (PC to PC, switch to switch). Note: Modern Gigabit Ethernet and above use auto-MDIX, which automatically detects and adjusts for straight-through or crossover cables, making crossover cables largely obsolete. Auto-MDIX: Why Crossover Cables Are Obsolete Auto-MDIX (Automatic Medium-Dependent Interface Crossover) is a feature introduced in the Gigabit Ethernet standard (1000Base-T) that automatically detects whether the connected port needs a straight-through or crossover connection and adjusts accordingly. Since 1000Base-T uses all 4 pairs bidirectionally, the PHY can dynamically assign transmit and receive pairs. This means you can use a straight-through cable for all connections, regardless of device type. RJ45 Pinout by Ethernet Speed Speed Pairs Used Pins Active Notes 10Base-T 2 (TX and RX) 1, 2, 3, 6 Only 4 pins active; pins 4,5,7,8 unused 100Base-TX 2 (TX and RX) 1, 2, 3, 6 Same pinout as 10Base-T; higher frequency 1000Base-T 4 (all bidirectional) 1, 2, 3, 4, 5, 6, 7, 8 All 8 pins active; auto-MDIX mandatory 2.5G/5GBase-T 4 (all bidirectional) 1, 2, 3, 4, 5, 6, 7, 8 Same pinout; higher signaling rate 10GBase-T 4 (all bidirectional) 1, 2, 3, 4, 5, 6, 7, 8 Same pinout; requires Cat6a+ cable PoE Pinout: How Power Is Delivered Over RJ45 Power over Ethernet (PoE) delivers DC power over the same RJ45 cable that carries data. There are two modes defined by IEEE 802.3: Mode A (Phantom Power) Power is delivered on the same pins as data (pins 1-2 and 3-6). The DC voltage is superimposed on the data signal using center-tapped transformers. This is the most common mode for 802.3af and 802.3at. Mode B (Spare Pair Power) Power is delivered on the unused pairs (pins 4-5 positive, pins 7-8 negative). In 10/100Base-T, these pairs are unused for data, making Mode B simple. In Gigabit Ethernet, all pairs carry data, so Mode B also uses center-tapped transformers. PoE++ (802.3bt Type 3 and 4) PoE++ uses both Mode A and Mode B simultaneously to deliver up to 90W. All 4 pairs carry both data and power. The center tap of each transformer carries the DC current. This requires ICM RJ45 connectors with magnetics rated for the full PoE current. Common RJ45 Wiring Mistakes Mistake 1: Mixing T568A and T568B on a Straight-Through Cable If one end is T568A and the other is T568B, you have accidentally created a crossover cable. On older 10/100Base-T equipment without auto-MDIX, this will prevent link establishment. Always verify both ends use the same standard for straight-through cables. Mistake 2: Splitting Pairs Across Non-Adjacent Pins In 10/100Base-T, pins 3 and 6 must be the same pair (green or orange). A common mistake is to wire pins 3, 4, 5, 6 sequentially with 4 different wires, splitting the pair. This causes excessive crosstalk and can prevent the link from working at 100 Mbps. Mistake 3: Untwisting Too Much Cable Twisted pairs rely on the twist to cancel electromagnetic interference. If you untwist more than 13mm (0.5 inch) of wire at the connector, the crosstalk performance degrades significantly, especially at Gigabit speeds. Keep the twist as close to the connector as possible. Mistake 4: Using the Wrong Cable Category A Cat5e connector on Cat6 cable (or vice versa) creates an impedance mismatch. The wire gauge and twist rate differ between categories, so always match the connector to the cable category. Using a Cat5e connector on a Cat6 cable will limit performance to Cat5e levels. VITALCONN ICM RJ45: Pre-Wired for Compliance When you use VITALCONN's ICM (Integrated Connector with Magnetics) RJ45 connectors, the pinout and wiring are already handled internally. The magnetic module is pre-wired to the correct pins according to IEEE 802.3 standards, ensuring compliance and eliminating wiring errors. You only need to connect the PCB traces to the connector's through-hole or SMT pads according to the datasheet pinout. Advantages of using ICM RJ45 instead of discrete magnetics: No risk of wiring mistakes — the magnetics are factory-tested and pre-wired Guaranteed IEEE 802.3 compliance for insertion loss, return loss, and crosstalk Simplified PCB layout — no need to place and route discrete transformers PoE center taps are pre-configured for Mode A and/or Mode B EMI shielding is integrated into the connector housing VITALCONN offers 163+ ICM RJ45 models covering T568A/T568B compatible pinouts, with speeds from 10/100M to 10G and PoE support up to 90W. Our ARP platform also provides 26 cross-reference replacements for Pulse, BelFuse, TE, and Molex RJ45 connectors. 💡 Tip:Using VITALCONN ICM RJ45 connectors eliminates wiring errors entirely — the magnetics are factory-tested and pre-wired to IEEE 802.3 standards. With 163+ models and 26 ARP cross-reference replacements, you get 30-40% cost savings and 2-4 week lead times. Frequently Asked Questions (FAQ) What is the difference between T568A and T568B? The only difference is the color assignment of the orange and green pairs. In T568A, the green pair is on pins 1-2 and the orange pair is on pins 3-6. In T568B, it is reversed: the orange pair is on pins 1-2 and the green pair is on pins 3-6. Both standards are functionally identical and deliver the same performance. Which pins are used for 10/100Base-T? Only 4 pins are active: pins 1 and 2 (TX+ and TX-), and pins 3 and 6 (RX+ and RX-). Pins 4, 5, 7, and 8 are unused in 10/100Base-T. Note that pins 3 and 6 must be the same twisted pair. Which pins are used for Gigabit Ethernet (1000Base-T)? All 8 pins are active in 1000Base-T. Each of the 4 twisted pairs carries bidirectional data simultaneously using hybrid echo cancellation. The pinout is the same as T568A or T568B, but all 4 pairs are used. How does PoE work with the RJ45 pinout? PoE delivers DC power over the RJ45 cable using center-tapped transformers. In Mode A, power is on pins 1-2 (positive) and 3-6 (negative). In Mode B, power is on pins 4-5 (positive) and 7-8 (negative). PoE++ (802.3bt Type 3/4) uses both modes simultaneously to deliver up to 90W. Can I use a T568A cable with a T568B jack? Yes, as long as both ends of the cable use the same standard (both T568A or both T568B). The jack on the equipment does not care whether the cable was wired T568A or T568B, because the signal is on the same pins regardless of color. The color standard only matters for consistency during installation. Need ICM RJ45 Connectors for Your Next Project? VITALCONN manufactures 163+ ICM RJ45 models with pre-wired IEEE 802.3 compliance, PoE up to 90W, and ISO 9001 certified quality. Request free samples or a custom quote today. Explore ICM RJ45 Request Samples