RJ45 / Ethernet (T568A & T568B) Pinout
The 8-pin (8P8C) Ethernet jack — wiring order for T568A and T568B.
Overview
An Ethernet jack is an 8-position, 8-contact (8P8C) connector, almost always called RJ45. The eight pins carry four twisted pairs. The TIA/EIA-568 standard defines two pin-to-color wiring schemes, T568A and T568B; both are electrically identical — what matters is that both ends of a cable use the SAME scheme (a straight-through cable). T568B is the most common in practice.
On 10/100 Mbit Ethernet only two pairs are used: pins 1–2 transmit and pins 3–6 receive. Gigabit (1000BASE-T) uses all four pairs bidirectionally (BI_DA…BI_DD). Power over Ethernet (PoE) injects DC onto the pairs.
Pin 1 is on the left when you hold the plug with the clip facing away from you and the contacts toward you.
Pinout
| Pin | Name | Function | Description |
|---|---|---|---|
| 1 | TX+ / BI_DA+ | PAIR / DATA | Pair 2 +. T568B white/orange, T568A white/green. 10/100 transmit+. |
| 2 | TX− / BI_DA− | PAIR / DATA | Pair 2 −. T568B orange, T568A green. 10/100 transmit−. |
| 3 | RX+ / BI_DB+ | PAIR / DATA | Pair 3 +. T568B white/green, T568A white/orange. 10/100 receive+. |
| 4 | BI_DC+ | PAIR | Pair 1 +. Blue. Gigabit only / PoE. |
| 5 | BI_DC− | PAIR | Pair 1 −. White/blue. Gigabit only / PoE. |
| 6 | RX− / BI_DB− | PAIR / DATA | Pair 3 −. T568B green, T568A orange. 10/100 receive−. |
| 7 | BI_DD+ | PAIR | Pair 4 +. White/brown. Gigabit only / PoE. |
| 8 | BI_DD− | PAIR | Pair 4 −. Brown. Gigabit only / PoE. |
Notes
- T568A vs T568B only swaps the orange and green pairs (pins 1-2 ↔ 3-6 colors). Pick one and use it on both ends for a straight-through cable.
- A crossover cable wires T568A on one end and T568B on the other (rarely needed now — modern ports auto-MDI-X).
- 10/100 Mbit uses only pairs on pins 1-2 and 3-6; Gigabit uses all four pairs.
Reference: TIA/EIA-568 wiring standard· verified 2026-06-21