Ethernet Distance Limits — The 100 m Rule
The twisted-pair distance rules from TIA-568 and IEEE 802.3: the 100 m channel and its 90 + 10 decomposition, the applications that run shorter, and the patch-cord fine print. The channel model is a TIA (voluntary-standard) construct; the rates at distance are IEEE interoperability specs. PoE at any power level changes none of these lengths.
Maximum distance by application
| Application | Cable | Max distance | Basis |
|---|---|---|---|
| 10BASE-T / 100BASE-TX / 1000BASE-T | Cat5e or better | 100 m channel | IEEE 802.3 + TIA-568 |
| 2.5GBASE-T | Cat5e or better | 100 m channel | IEEE 802.3bz |
| 5GBASE-T | Cat6 or better | 100 m channel | IEEE 802.3bz |
| 10GBASE-T | Cat6 | 37 m (55 m favorable alien-crosstalk) | TIA TSB-155 |
| 10GBASE-T | Cat6A | 100 m channel | IEEE 802.3an + TIA-568 |
| 25GBASE-T / 40GBASE-T | Cat8 | 30 m channel, 2 connectors | IEEE 802.3bq + TIA-568.2-D |
Channel vs permanent link — why the 100 splits 90/10
The permanent link is what gets built into the walls: up to 90 m of solid-conductor horizontal cable, jack to patch panel, and it is what a certification tester qualifies. The channel adds the stranded cords on both ends — up to 10 m combined — for 100 m total. Stranded cord loses more signal per meter than solid horizontal, which is exactly why the budget is split rather than being a single 100 m anywhere. Design pulls to 90 m, not 100: a “97 m pull, short cords” plan fails the day someone patches with a 5 m cord.
The 28 AWG skinny cords popular in dense racks tighten this further: each meter counts as 1.95 m of budget, capping cordage near 6 m on a full link and 15 m overall. The often-quoted “7 m” rounds the formula the wrong way — the insertion-loss math gives 6 m.
Past 100 m
Three clean options, in the order estimators usually price them: an intermediate switch or PoE extender (each hop resets the budget), fiber with media converters (kilometers of headroom — and the right answer for anything between buildings), or moving the telecom room. For powered endpoints past the limit, note that PoE extenders need the power budget to survive the extra hop — check the PoE wattage chart. For category selection at distance, see the category comparison.
Common questions
What is the maximum distance for ethernet cable?
100 meters (328 ft) for the channel — but that number decomposes: 90 m of solid-conductor permanent link in the walls plus 10 m total of stranded patch and equipment cords across both ends, per TIA-568. A 100 m horizontal pull with cords added on top is already out of spec.
What happens if an ethernet run is longer than 100 m?
The link often still comes up — autonegotiation typically works and may downshift to a lower speed — but insertion loss and crosstalk exceed the limits the electronics were designed for, so bit errors and retransmissions rise, and the run can never be certified. The clean fixes: fiber with media converters, a PoE extender or intermediate switch (each hop resets the 100 m budget), or relocating the equipment room.
How far can Cat6 run 10 Gbps?
37 m guaranteed, and up to 55 m only in a favorable alien-crosstalk environment (few neighboring cables, unbundled) per TIA TSB-155. For 10GBASE-T at the full 100 m, the answer is Cat6A. This is the most common distance surprise in the field — Cat6 is a 100 m cable at 1/2.5/5 Gbps, not at 10.
Do skinny 28 AWG patch cords change the length budget?
Yes — 28 AWG cords lose signal faster, so TIA-568.2-D counts each meter of them as 1.95 m against the cord budget. With a full 90 m permanent link that leaves about 6 m of 28 AWG cordage (a ~96 m channel), and regardless of link length, total 28 AWG cordage should stay under 15 m per channel for DC resistance. Horizontal cable in the walls stays 22–24 AWG solid — 28 AWG is a patch-cord gauge only.
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