When you need a stable, high-speed connection, the cable matters. Are all Ethernet cables the same? No—and choosing the wrong one can limit speed, shorten maximum length, introduce interference, or complicate PoE. Ethernet cables are a type of network cable used to connect devices within data networks, and there are different types of network cables designed for various networking needs.
All Ethernet cable categories are designed with specifications that determine their maximum transmission speeds and distances, with different types of Ethernet cables supporting the requirements of modern data networks. This guide explains Ethernet cable categories, twisted pair options (UTP vs STP), maximum lengths, shielding, and UK-specific considerations so you can pick the right cable the first time.
TL;DR (Quick answer)
- Cat5e is fine for most Gigabit Ethernet up to 100 m. Cat5e was commonly used for Fast Ethernet (100 Mbps) and can support speeds up to 1 Gbps depending on cable quality and length.
- Cat6 supports 10 GbE up to ~55 m (full 100 m at 1 GbE) and is a common, cost-effective step up. Cat6 cables support speeds up to 10 GbE over shorter distances.
- Cat6a is safe, has 10 GbE up to 100 m choice, and has a strong “future-proof” default for new installations. It supports 10 Gigabit Ethernet over a full 100-meter channel and has a maximum frequency of 500 MHz.
- Cat7 (ISO/IEC Class F) is not a TIA/EIA standard and is rarely necessary in offices/homes; it’s typically fully shielded and niche.
- Cat8 targets 25/40 GbE in short data-centre runs (≈30 m channel). Cat8 is typically used for switch-to-switch connections in data centre environments, supporting very high data speeds. Not for general building horizontal cabling.
- UTP (unshielded twisted pair) suits most offices/homes. STP/FTP/S/FTP helps in high-EMI environments (machinery rooms, comms rooms with dense bundles).
- Don’t exceed 100 m for permanent links (copper). Keep patching sensibly.
Ethernet cable categories (Cat5e → Cat8) explained
Ethernet cable categories define performance (bandwidth/frequency), shielding, wiring, and test limits. The cable category determines the maximum data transmission rates and the quality of signals that can be maintained over different distances.
Higher category cables generally offer higher bandwidth, better resistance to crosstalk/interference, and improved wiring with tightly twisted wires to reduce crosstalk and support higher data rates—applicable for larger networks, video conferencing, and high-speed data transfer. Higher category Ethernet cables generally support faster speeds, with Cat6 and above capable of handling 10 Gbps or more speeds.
Choosing the right cable category and wiring standard is essential for reliable data transmission and maintaining signal integrity.
Cat5e
- Typical use: Home network, small offices; Gigabit Ethernet up to 100 m.
- Pros: Affordable, easy to terminate.
- Consider: It can be limited to 10 GbE or noisy environments. For example, Cat5e may not support 10 GbE connections or may experience crosstalk interference in areas with significant electrical noise.
Cat6
- Typical use: SMB offices needing headroom; 10 GbE up to ~55 m under worst-case bundling; 1 GbE to 100 m.
- Pros: Uses tighter twisted pairs for better performance, providing better signal quality and reduced crosstalk than Cat5e.
- Consider: If you genuinely need 10 GbE to 100 m, jump to Cat6a.
Cat6a
- Typical use: New builds/refits; 10 GbE to 100 m; better for PoE (802.3af/at/bt) due to thicker conductors and thermal characteristics. Commonly chosen for business networks with demanding network requirements to ensure optimal performance and future-proofing.
- Pros: Higher performance, higher bandwidth, robust alien-crosstalk control.
- Consider: Slightly thicker cable; plan pathways accordingly.
Cat7 (ISO/IEC Class F)
- Typical use: Niche; fully shielded systems, sometimes non-RJ45 interfaces.
- Pros: Improved shielding (foil shielding and/or braid); individual pairs are often shielded.
- Consider: Not officially recognised by TIA for building cabling; compatibility and connector ecosystem can be awkward in UK office fit-outs.
Cat8
- Typical use: Primarily deployed in data centres for switch-to-server or ToR (top-of-rack) links; recognised as the latest standard in the networking industry; 25/40 GbE; ≈30 m channel.
- Pros: Very high speed for short cable runs.
- Consider: Not for typical floor-to-desk runs; costly and over-spec for normal workplaces.
Tip: For most UK premises, Cat6a UTP is the “installed once, used for a decade” sweet spot. It balances performance, cost, and compatibility with standard network equipment.
Twisted pair basics: UTP vs STP (and when shielding helps)
Twisted pair cables work by cancelling electromagnetic interference through tight twisting of the pairs. The wires inside Ethernet cables are twisted together as key components to minimise interference and improve performance.
The twist rate of the conductor pairs in an Ethernet cable helps minimise signal interference and crosstalk, improving cable performance. You’ll see two broad families:
- UTP (unshielded twisted pair) – lighter, cheaper, easier to terminate; ideal for most wired networks.
- STP/FTP/S/FTP (shielded twisted pair) – adds cable shielding (overall foil/braid and/or individual pair foil) to reduce interference, radio frequency interference, and improve signal quality in harsh environments.
When to choose shielding:
- Near machinery, UPS rooms, lifts, fluorescent/LED drivers, or large bundles.
- In data centres (data centre) with dense high-speed links.
- For long PoE runs where thermal and noise margins matter.
If your space is a typical office with sensible pathways, UTP is usually perfect.
Ethernet Cable Selector Tool
Use our bespoke tool below to workout what ethernet cable(s) you need for your home or office project.
Ethernet Cable Selector
Answer a few quick questions to see the right cable category and shielding for your run. We’ll give you an explanation and alternatives.
Is Cat7 or Cat8 a better choice than Cat6a?
Short answer: For office and general building cabling, Cat6a is the recommended standard. It supports 10 Gb/s up to 100 m with better PoE headroom and broad RJ45 compatibility.
- Cat7/7a: ISO/IEC classes (F/FA) typically expect GG45/TERA connectors, not standard RJ45. Many retail “Cat7” patch leads are just heavily shielded Cat6 variants.
- Cat8: Designed for short data-centre links (around 30 m) at 25/40 Gb/s. It’s shielded-only and not intended for horizontal office runs.
- Future-proofing: If you’re planning 7+ years or heavy PoE/EMI/bundling, Cat6a is usually the sweet spot. For long backbones or >10 Gb/s across floors, go fibre.
Want a tailored design? Send your answers to RJ Electrical Contractors — we’ll confirm the spec and costs.
No obligation. We’ll review your use case and recommend the right cabling and containment.
Key UK considerations (standards, LSZH, outdoor use)
- Standards: UK specifications generally align to BS EN/ISO/IEC (e.g., ISO/IEC 11801, BS EN 50173). Following these recognised standards also helps ensure network security and compliance. Note Cat7 is ISO/IEC Class F and not a TIA-recognised building standard, hence limited use in typical commercial fit-outs.
- Sheathing: For internal routes, LSZH (Low Smoke Zero Halogen) is often preferred/required over PVC for safety.
- Outdoor use: Use UV-rated outdoor cable and follow best practices for earthing/shielding and moisture barriers.
- Pathways: Cat6a is thicker; plan trays/conduits accordingly to maintain bend radius and avoid physical damage.
Comparison table: speed, length, frequency, shielding
| Category | Typical Bandwidth/Frequency | Common Speed & Max Length | Shielding (default) | Connector Ecosystem | Best For |
|---|---|---|---|---|---|
| Cat5e | Up to ~100 MHz | 1 GbE to 100 m | UTP | RJ45 throughout | Home networks, budget desks, peripherals |
| Cat6 | 250 MHz | 10 GbE up to ~55 m; 1 GbE to 100 m | UTP or shielded variants | RJ45 throughout | SMB offices needing headroom |
| Cat6a | 500 MHz | 10 GbE to 100 m | UTP/FTP/S/FTP | RJ45 throughout | New builds, heavy PoE, future-proofing |
| Cat7 (Class F) | 600 MHz+ | Varies; not a TIA building standard | Typically fully shielded | Often non-standard connectors in spec | Niche, special environments |
| Cat8 | 2000 MHz | 25/40 GbE up to ≈30 m channel | Shielded | RJ45 in Cat8.1 ecosystem | Data centre switch/server links |
Real-World Scenarios
Home network (work-from-home, streaming, gaming)
- Goal: stable Gigabit Ethernet, low latency, tidy cabling, and reliable connections for every device in the home.
- Pick: Cat6 UTP as a practical baseline, or Cat5e if budget-tight and runs are simple.
- Why: Plenty for internet connection needs and local transfers; easy to terminate.
SME office (dozens of desks, VoIP, Wi-Fi 6/6E APs, video conferencing)
- Goal: keep uplinks/APs happy; ensure reliable communications across the office network; PoE for phones/APs/cameras.
- Pick: Cat6a UTP to the desk and APs/cameras.
- Why: Higher performance; 10 GbE to 100 m if needed later; better thermal for PoE.
Data centre/comms room (short switch-to-server)
- Goal: high-speed data transfer over short cable runs.
- Pick: Cat8 for ≤30 m channels (25/40 GbE) or move to fibre where appropriate.
- Why: Cat8 cables are chosen to support the speeds required for modern data centre operations. Copper at very high rates is distance-limited; plan for structured fibre backbones.
FAQs
How do I know which Ethernet cable I need?
Match environment (EMI?), speed, and distance. For general UK offices, Cat6a UTP is a strong default; homes often use Cat6 or Cat5e.
Can I use any Ethernet cable?
You can connect devices with most RJ45 leads, but performance and reliability vary. Lower categories may cap speed or struggle with interference over long runs.
Should I get a Cat7 or Cat8 Ethernet cable?
Cat7 is ISO/IEC Class F and not widely used in UK offices; Cat8 is for short data-centre links. For buildings and desks, Cat6a is typically the correct answer.
How do you know if an Ethernet cable is compatible?
Ethernet is backwards compatible: a higher category cable (e.g., Cat6a) works with older network equipment, but you only get the speed the endpoints support.
Does cable length affect speed?
Yes. Keep horizontal runs ≤100 m (including patching within limits). For 10 GbE on Cat6, real-world support drops after ~55 m; Cat6a keeps 10 GbE to 100 m.
Do I need shielded twisted pair?
Use shielded twisted pair where external electromagnetic interference is likely (machinery, dense bundles). Else, unshielded twisted pair is simpler and cost-effective.
Is outdoor use different?
Yes—look for outdoor-rated jackets, correct earth bonding for shielded systems, and weatherproof terminations.
