Ethernet cables explained: Cat 5e, Cat 6, Cat 6a, Cat 7, Cat 8

By The SpeedFibre team, updated . 3 min read.

Ethernet cables explained: Cat 5e, Cat 6, Cat 6a, Cat 7, Cat 8
In short For gigabit internet, Cat 5e or Cat 6 is enough. For 2.5 or 5 Gbps, Cat 5e and Cat 6 still work up to 100 m. For 10 Gbps, choose Cat 6a. If your wired test is stuck around 94 Mbps, a damaged cable or a 100 Mbps port is almost always the reason.
Contents
  1. The categories in one table
  2. The 94 Mbps trap
  3. Flat, thin and long cables
  4. Do you need Cat 7 or Cat 8?
  5. Testing the right way

A cable test is the most reliable way to measure your internet speed, but only if the cable itself is not the bottleneck. The category printed on the cable jacket tells you what it can carry.

The categories in one table

CategoryRated forMax length at that speedGood for
Cat 5100 Mbps100 mAvoid: caps you at about 94 Mbps
Cat 5e1 Gbps (2.5 Gbps)100 mGigabit internet, most homes
Cat 61 Gbps, 5 Gbps, 10 Gbps100 m, 100 m, 55 mGigabit and multi-gig
Cat 6a10 Gbps100 m10 Gbps fibre, future-proof wiring
Cat 7 / 7a10 Gbps100 mShielded, uncommon connectors; Cat 6a is usually simpler
Cat 825 to 40 Gbps30 mData centres, not useful at home

The 2.5 and 5 Gbps speeds come from the IEEE 802.3bz standard, designed precisely so existing Cat 5e and Cat 6 wiring could carry multi-gigabit speeds.

The 94 Mbps trap

If a cable test gives between 90 and 95 Mbps on a plan that should be much faster, your connection has fallen back to Fast Ethernet (100 Mbps). Common causes:

  • an old Cat 5 cable, or a cable with a damaged pair (gigabit needs all four pairs, 100 Mbps only two);
  • a 100 Mbps port on an old computer, switch, TV box or powerline adapter;
  • a bent, crushed or poorly crimped connector.

Check the link speed: on Windows, open Settings > Network > Ethernet and look at "Link speed"; on macOS, hold Option, click the network menu and read the speed. It should say 1000 Mbps (or 2.5 Gbps) for a gigabit plan.

Flat, thin and long cables

Flat and very thin cables are convenient under rugs and doors and usually work fine for 1 Gbps over a few metres. For long runs inside walls, choose a round, solid-copper cable from a known brand; cheap "copper-clad aluminium" (CCA) cables can fail certification and cause errors. Length up to 100 m is never an issue in an apartment.

Do you need Cat 7 or Cat 8?

Almost never at home. Cat 7 uses shielding and was designed around different connectors, and Cat 8 targets very short data-centre links. A good Cat 6 or Cat 6a cable covers everything up to 10 Gbps internet.

Measure your connection now. Start the test

Testing the right way

  1. Plug the computer directly into the router with a Cat 5e or better cable.
  2. Check the link speed as explained above.
  3. Run a speed test three times and keep the middle value.
  4. Compare with Wi-Fi: the gap shows how much your wireless network costs you. See fibre slow on Wi-Fi, fast on Ethernet.
  5. On a multi-gig plan, make sure the router and the computer both have 2.5G or 10G ports: read is gigabit internet worth it.

#FiberSpeedTest#SpeedTest#WiFi

Sources and further reading

Frequently asked questions

Is Cat 6 faster than Cat 5e for internet?

Not for a 1 Gbps plan: both carry gigabit without trouble. Cat 6 matters above 2.5 Gbps or for long runs in electrically noisy places.

Why does my wired test show 94 Mbps?

Your link has negotiated 100 Mbps instead of 1 Gbps. Replace the cable first, then check that every device in the chain has a gigabit port.

Can an Ethernet cable be too long?

Above 100 m, yes. Inside a home you will never get close to that limit.

The SpeedFibre team Guides written and reviewed by a telecom engineer specialised in fibre optics (FTTH), with more than 8 years of hands-on network maintenance and measurement. Editorial policy.

Related guides