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How to Extend an Ethernet Cable
The simplest way to extend an Ethernet cable is to join two lengths together using an RJ45 inline coupler, which connects two patch leads socket-to-socket without any loss of signal quality — provided your total cable run stays under 100 metres. For a cleaner, more reliable result, replacing both short cables with a single longer cable is often the better fix. If you need to go beyond 100m, you'll need to add a network switch part-way along the run rather than simply joining more cable.
Step-by-Step: Choosing the Right Extension Method
1. Check your total cable length first
Ethernet (Cat5e/Cat6/Cat6A) has a hard limit of 100 metres per run before signal degrades. Add up your existing cable plus whatever you're adding — if you're already close to 90-100m, a coupler won't help; you'll need a switch instead.
2. Joining two ready-made patch cables
For most home and office setups, an RJ45 inline coupler is the quickest solution. It's a socket-to-socket adapter that plugs onto both cable ends — no tools, no crimping.
CAT6 RJ45 Coupler GIGABIT Joiner Socket to Socket Adapter
£1.12Available in 6 options from £0.80 — See all variations
Gigabit-rated coupler for joining two standard patch cables end to end.
View Product3. Extending shielded cable (FTP/STP)
If your existing cable is shielded (common in offices near electrical interference), use a matching shielded coupler to maintain that protection.
Shielded CAT6 RJ45 Inline Coupler Joiner
£1.61Available in 6 options from £0.80 — See all variations
Maintains shielding continuity when extending FTP/STP cable runs.
View Product4. Extending solid-core cable in walls or trunking
Patch cables use stranded core and aren't designed for permanent installation. If you're joining solid-core cable behind walls, use a punch-down coupler instead — it terminates the wires properly rather than relying on a plug.
Inline Punch Down Coupler CAT6 Black
£2.11Available in 2 options and 2 colours from £1.72 — See all variations
Our best-selling coupler — ideal for permanently joining solid-core Cat6 in fixed installations.
View Product5. Extending cable outdoors
Never use a standard indoor coupler outside. An IP68-rated coupler seals the join against water and dust for garden, garage, or outbuilding runs.
External Outdoor Cat6 RJ45 IP68 Coupler
£4.88Available in 2 options from £4.88 — See all variations
Our top-selling coupler overall — fully waterproof and weatherproof for outdoor joins.
View Product6. Replacing with one longer cable
Every coupler introduces a joint, and joints are the most common source of connection problems. If you're extending by a large amount, or the run is important (a main office link, for example), it's often better to simply buy one longer cable and remove the joins altogether.
Cat6A SSTP Shielded RJ45 10GIG Cable 20m
£17.82Available in 11 lengths and 2 colours from £0.86 — See all variations
Shielded 10-gigabit cable in a single 20m length — no joints, no weak points. Also available in other lengths.
View Product7. Going beyond 100 metres
Ethernet cannot simply be joined past 100m — the signal won't hold. Instead, install a network switch part-way along the run: run up to 100m of cable to the switch, then continue a fresh 100m run from the switch onward. This also gives you extra ports if you need to connect multiple devices.
Mercusys 5 Port Gigabit Switch
£12.13Regenerates the Ethernet signal for a fresh 100m run and adds extra ports for more devices.
View ProductComparison: Which Extension Method Should You Use?
| Method | Best For | Distance Limit | Price From |
|---|---|---|---|
| RJ45 inline coupler | Joining two patch cables | Counts towards 100m total | £1.12 |
| Shielded inline coupler | Joining shielded FTP/STP cable | Counts towards 100m total | £1.61 |
| Punch-down coupler | Permanent joins of solid-core cable | Counts towards 100m total | £2.11 |
| IP68 outdoor coupler | Joins outside or in damp areas | Counts towards 100m total | £4.88 |
| Single longer cable | Avoiding joints altogether | Up to 100m in one length | £17.82 |
| 5-port gigabit switch | Runs beyond 100m or extra devices | Resets to a new 100m run | £12.13 |
Common Mistakes to Avoid
- Never twist bare wires together. This isn't a reliable connection and will cause intermittent faults, signal loss, or complete failure — always use a proper coupler.
- Don't chain multiple couplers. One coupler joining two cables is fine, but each extra joint adds resistance and risk of interference — if you need several joins, use one longer cable instead.
- Don't exceed 100m total. This includes all cable segments plus couplers — going over this limit causes dropouts even if everything is wired correctly.
- Don't use an indoor coupler outside. Moisture ingress will corrode the contacts — always use an IP68-rated coupler outdoors.
If your run is close to 100m already, a coupler is a false economy — a network switch or a single fresh cable will give a far more reliable connection.
Related Questions
Can I just join two Ethernet cables together?
Yes — use an RJ45 inline coupler to join two patch cables, or a punch-down coupler for solid-core cable. Avoid twisting wires together, as this is unreliable.
How far can an Ethernet cable be extended?
Up to 100 metres total per run, including any couplers or joins. Beyond that, you need a network switch to regenerate the signal for a further 100m run.
Does joining Ethernet cables reduce speed?
A single, well-made coupler join has no noticeable effect on Gigabit speeds. Multiple joins or poor-quality connections can introduce interference and packet loss.
Is it better to join cables or buy one longer cable?
For short extensions, a coupler is quick and cheap. For longer or important runs, a single cable (available in various lengths) avoids joints entirely and is more reliable.