Example 1: checking a patch cable
If both ends follow T568B in the same orientation, the cable is a standard straight-through patch lead. The reference helps confirm the pin and color order before you reach for a cable tester.
SpecCalc Hub
RJ45 T568A/B Pinout Reference
Original diagram for T568A and T568B pair order.
What this page helps with
T568A and T568B describe two standard pin assignments for 8P8C Ethernet-style terminations commonly called RJ45 in practice. The key difference is the pair order on certain pins, not the basic connector shape.
This page is useful when crimping patch leads, checking wall outlets or diagnosing why one cable end does not match the other.
Formula or method
The page is structured as a practical reference: start with the visible table, diagram and labels, then compare them with the exact connector, device, enclosure or symbol set in front of you.
Use the listed sources to confirm revision, naming and application context. Similar labels can hide different electrical limits, pin functions or test conditions, so the page should be treated as a guided reference rather than a universal standard text.
How to use
- Read the pin numbers in the same orientation every time, otherwise a correct cable can look wrong on paper.
- Compare the color order on both ends and confirm whether both ends are A, both ends are B or one end differs from the other.
- Use the pinout as a wiring reference only. Certification, bandwidth and PoE suitability still depend on cable quality and testing.
Practical examples
Example 2: mixed A/B termination
If one end is T568A and the other is T568B, the pair mapping changes. Historically that indicated a crossover-style behavior in certain contexts, so the mixed termination should be intentional rather than accidental.
Common mistakes
- Reading the connector backwards and swapping left-right orientation.
- Mixing T568A and T568B unintentionally on opposite ends.
- Assuming a correct pinout means the cable is certified for the target speed.
Limitations
- This page is a wiring reference, not a network certification result.
- Cable category, twist integrity and termination quality still matter.
- Check equipment requirements and testing practice before real deployment.
FAQ
Is T568B better than T568A?
Not inherently. The important thing is consistency with the project or building standard.
Does this page certify Ethernet performance?
No. It only helps with pin order and orientation.
Why can the same colors look wrong?
Because reversing connector orientation makes a correct order appear mirrored.
Related tools
Last reviewed: 2026-06-05
Factual reference
RJ45 T568A/B
Verify the current manufacturer documentation, product standard and local rules before real use.
| Pin | T568A | T568B | Pair |
|---|---|---|---|
| 1 | white/green | white/orange | 3 / 2 |
| 2 | green | orange | 3 / 2 |
| 3 | white/orange | white/green | 2 / 3 |
| 4 | blue | blue | 1 |
| 5 | white/blue | white/blue | 1 |
| 6 | orange | green | 2 / 3 |
| 7 | white/brown | white/brown | 4 |
| 8 | brown | brown | 4 |
This calculator provides an estimate for informational purposes only. It is not a certified engineering design, electrical safety approval, or professional installation recommendation. Always verify final decisions with a qualified professional and applicable local codes.