Longest Ethernet Cable: 100 Metres, Then Something Else
Quick answer / TL;DR: Short answer: the maximum channel length for Cat5e, Cat6 and Cat6a is 100 m, made up of up to 90 m of permanent link plus 10 m of patch cords in total. Beyond 100 m, use fibre or a copper extender. Buying a 150 m Cat6 cable does not extend the standard; it just creates an out-of-specification link.
Length tiers: patching, desk, room, cross-room, floor – each with its own SKU.Twisted-pair Ethernet has a hard channel limit of 100 metres. Beyond it, the link may come up but will not meet the standard it claims.
The limit is a channel limit, not a cable limit, which is why patch cords count against it.
How the Budget Works
| Element | Allowance | Note |
|---|
| Permanent link | 90 m | Cable in the building |
| Patch cords | 10 m total | Both ends combined |
| Channel | 100 m | The standard limit |
| Beyond | Fibre or extender | Not a longer copper cable |
The patch allowance is shared, so two 8 m patch cords plus a 90 m run is 106 m and out of specification before anything is measured.
What Actually Happens Beyond 100 m
- The link may negotiate at a lower speed
- Some switches will not bring the port up at all
- Error rates rise before the link fails
- PoE voltage drop increases
A link that comes up at 100 Mbps instead of 1 Gbps is a classic symptom of an over-length run.
Real-World Applications
A workshop 130 m from the switch needs fibre or a copper extender, not a longer Cat6 reel. A 95 m run with two 3 m patch cords is already at 101 m and should be re-planned before installation.
Standards and Verification
| Reference | Relevance |
|---|
| TIA-568.2-D | Channel and link limits |
| ISO/IEC 11801 | Generic cabling |
| IEEE 802.3 | Ethernet PHY specifications |
Measured performance of a specific installation is not provided in the knowledge base. Certify the link with a field tester.
Practical Notes
Record every run length. A drawing with lengths is the difference between a five-minute diagnosis and a day of swapping cables.
Related reading: ethernet cable — blogs/news/ethernet-cable
Related reading: white ethernet cable — blogs/news/white-ethernet-cable
Related reading: weatherproof ethernet cable — blogs/news/weatherproof-ethernet-cable
Frequently Asked Questions
What is the maximum length?
100 m channel for twisted-pair Ethernet.
Does a longer cable work?
It may link at reduced speed and is out of specification.
What do I use beyond 100 m?
Fibre or a copper extender.
Sourcing cables for a project, a store, or a private-label line? Contact our B2B sales team for specifications, certification evidence, and volume terms – FOB and CIF options available. Request a quote or sample.
