Ethernet Cable Length Calculator
Planning an Ethernet cable run requires knowing the maximum distance your cable category supports at the speed you need. The TIA-568 and IEEE 802.3 standards define the maximum segment length for each cable category and speed combination. Exceeding these limits causes signal degradation, higher error rates, and unreliable connections. The universally known 100-metre limit applies to most category and speed combinations, but there are important exceptions. Cat6 cable at 10 Gbps is limited to 55 metres due to alien crosstalk at higher frequencies. Cat8 cable, designed for data centre patch applications, is limited to 30 metres even at 40 Gbps. Cat6A addresses the Cat6 limitation by extending full 10 Gbps support to 100 metres through improved shielding and construction. Cat7 and Cat7A offer similar or better performance to Cat6A and are more commonly found in European installations. When a run exceeds the maximum for your category and speed combination, the solution is to install an intermediate switch or media converter, or to use fibre optic cable, which is not subject to the 100-metre copper limit. Select your cable category and target speed below to see whether a single run will work and what the maximum segment length is.
Ethernet cable category and speed reference table
Maximum segment length per TIA-568 and IEEE 802.3. "N/S" means "not supported" by this cable category at that speed.
| Cable | 100 Mbps | 1 Gbps | 2.5 Gbps | 5 Gbps | 10 Gbps | 25 Gbps | 40 Gbps |
|---|---|---|---|---|---|---|---|
| Cat5e | 100 m | 100 m | N/S | N/S | 55 m* | N/S | N/S |
| Cat6 | 100 m | 100 m | 100 m | 100 m | 55 m | N/S | N/S |
| Cat6A | 100 m | 100 m | 100 m | 100 m | 100 m | N/S | N/S |
| Cat7 | 100 m | 100 m | 100 m | 100 m | 100 m | N/S | N/S |
| Cat8 | 30 m | 30 m | 30 m | 30 m | 30 m | 30 m | 30 m |
* Cat5e may support 10 Gbps up to 55 m in ideal conditions; not formally standardised for 10GBASE-T.
How to read the results
If the result shows a maximum segment length, a single cable run up to that length will support the selected speed. If the result shows "Not supported," the cable category cannot reliably carry the selected speed regardless of length. In that case, upgrade to a higher category cable or reduce the target speed. If your run exceeds the maximum for your combination, install an intermediate network switch to break the run into two segments, each within the limit.
Ethernet cable length: frequently asked questions
Why is the maximum Ethernet cable length 100 metres?
The 100-metre limit for Ethernet segments is defined in the TIA-568 and IEEE 802.3 standards. It is set by the signal attenuation and propagation delay characteristics of twisted-pair copper cabling. Beyond 100 metres, signal quality degrades to the point where reliable data transmission at standard speeds cannot be guaranteed. The 100 m limit includes both the horizontal cable run and any patch cables at either end, so a run from wall to switch should typically stay within 90 metres of structured cabling to leave room for 5 m of patch cable at each end.
Why does Cat6 drop to 55 metres at 10 Gbps?
Standard Cat6 cable is rated for 10 Gbps (10GBASE-T) only up to 55 metres, compared to its full 100-metre run at 1 Gbps. At 10 Gbps, the higher frequency signals are more susceptible to alien crosstalk (interference from adjacent cables in a bundle). Beyond 55 metres, the accumulated alien crosstalk causes enough errors to make 10 Gbps unreliable. Cat6A was designed specifically to support 10 Gbps to the full 100-metre distance by using improved shielding and separation between pairs.
Can I use a switch or repeater to extend Ethernet beyond 100 metres?
Yes. An Ethernet switch or media converter regenerates the signal, effectively resetting the distance counter. Each segment between two switches can be up to 100 metres. For longer runs, you can daisy-chain switches, though each switch adds latency. Alternatively, fibre optic cabling can run much longer distances (up to 550 metres for multimode and tens of kilometres for single-mode) without the 100-metre copper limitation. A network repeater (not a hub) also extends distance but is rarely used in modern networks.
What is the difference between shielded (STP) and unshielded (UTP) Ethernet cable?
Unshielded twisted pair (UTP) cable relies on the twist of each pair to cancel electromagnetic interference. Shielded twisted pair (STP or FTP) adds metallic foil or braid shielding around the pairs or the entire cable to provide additional protection against external interference. STP is preferred in environments with high electromagnetic interference (near heavy machinery, fluorescent lighting, or other cables). It requires proper grounding at both ends; improperly grounded STP can actually introduce more interference than UTP.
What is plenum-rated Ethernet cable and when is it required?
Plenum-rated cable (CMP in the US) is designed for installation in air-handling spaces such as the space above drop ceilings or below raised floors, where air circulates for HVAC purposes. Plenum cable uses a special low-smoke, flame-retardant jacket that, in the event of a fire, does not release toxic gases into the air circulation system. Building codes in the United States (per the National Electrical Code) require plenum-rated cable in plenum spaces. Standard (riser or PVC) cable may be used in other locations but not in plenum spaces.
Sources and methodology
- TIA-568 Telecommunications Cabling Standard: tiaonline.org.
- IEEE 802.3 Ethernet standard: ieee.org.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology. Real-world performance may vary depending on cable quality, installation conditions, and equipment. Consult a certified network engineer for critical infrastructure planning.