Ethernet Cable Reference
What each Ethernet category actually does, and how far it does it.
What you provide
Measure the whole path including patch leads at both ends, not the straight-line distance.
Result
Cat 6: 1 Gbps to 100 m, 10 Gbps to 55 m
The sensible default for new runs. Ten-gigabit works over shorter distances. Two things matter more than the number printed on the jacket: the termination, since a poorly punched-down keystone will fail at gigabit on a cable rated for ten, and whether it is solid or stranded core, because solid copper belongs in the wall and stranded belongs in a patch lead that gets moved. Copper-clad aluminium sold cheaply as Cat 6 meets none of this and is the usual cause of a run that will not do PoE.
- Category
- Cat 6
- Rated speed
- 1 Gbps to 100 m, 10 Gbps to 55 m
- Maximum runIncluding patch leads at both ends
- 100 m
- Bandwidth
- 250 MHz
- Power over Ethernet
- Up to PoE++ (60 W)
- Your runWithin specification
- 40 m
- 10 Gbps limit
- 55 m
What this cannot tell you
- A reference table for the standards, not a test of your cable. It cannot tell you whether a run is terminated correctly or whether the copper is what the jacket claims.
- Only a certification tester can confirm a run meets its category. A cheap cable tester checks continuity and pin order, which finds a miswired plug and misses almost everything else.
Take this with you
How this calculation works
Pick a category and enter the length of the run, and the guide shows the speed it carries, the distance it carries it, the bandwidth the standard specifies and the power class it supports. Your run is checked against the limit, and where a category supports ten gigabit only over a shorter distance, that second limit is shown separately. The 100 metre figure everyone quotes includes the patch leads at both ends, which is why measuring only the cable in the wall gets installations into trouble.
What the results mean
- Rated speed
- What the standard guarantees over a properly terminated run at full length. Shorter runs frequently do better, which is why 2.5 Gbps often works fine over existing Cat 5e.
- Maximum run
- The total channel length, patch leads included. Copper Ethernet stops at 100 metres in every category up to Cat 6a, and Cat 8 stops at 30.
- Bandwidth
- The frequency the cable is tested to, in MHz. Higher bandwidth is what lets a cable carry more data over the same distance, and it is the number that separates categories with identical speeds on paper.
Common problems and fixes
- A run negotiates at 100 Mbps instead of gigabit
- Almost always a termination fault rather than the cable. Gigabit uses all four pairs and 100 Mbps uses two, so a single bad pair drops the link a tier without breaking it. Re-terminate both ends, keeping the untwisting at the punch-down under about 13 mm, and check the wiring follows the same standard at both ends.
- PoE works on short runs but not long ones
- Suspect copper-clad aluminium. It is sold cheaply as Cat 6, meets none of the resistance requirements, and drops enough voltage over a long run that a powered device never comes up. Solid copper is the only thing that reliably carries power over distance. Strip a spare end and check the core: aluminium is silvery under the surface and snaps rather than bends.
Frequently asked questions
Is Cat 7 better than Cat 6a?
Not in any way that helps you. Cat 7 is not recognised by TIA, and in its true form it uses connectors that are not RJ45, which means anything sold as Cat 7 with normal plugs is Cat 6a wearing a better sticker. For a home or office run, Cat 6 or Cat 6a is the real choice.
Should I pull Cat 6 or Cat 6a?
Cat 6 for most buildings. It carries gigabit to the full 100 metres and ten gigabit to 55, which covers nearly every run in a normal building. Cat 6a earns its extra cost and stiffness where you genuinely need ten gigabit at distance, or where long PoE runs are feeding high-power devices.
Does shielded cable help?
Only in genuinely noisy environments, and only if it is grounded properly at one end. A shielded run terminated into unshielded keystones does nothing, and one grounded at both ends can create a current path that makes interference worse. In an ordinary office, good unshielded cable routed away from mains runs is the better choice.
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