Ethernet Cable Buying Guide: Cat6, Cat7, Cat8

Buying an Ethernet cable comes down to matching the cable category to your internet speed and the length you need. For most homes, a Cat6 cable up to 50 meters is the best balance of performance and cost, but the right choice depends on your network speed, future plans, and where the cable will run.

Formula

The calculator above works out the maximum speed your cable can support based on its length and the category you choose. The formula for the recommended category is a simple lookup based on speed:

• If your internet speed is 100 Mbps or less, Cat5e is sufficient.
• If your speed is between 100 and 1,000 Mbps, Cat6 is recommended.
• If your speed is above 1,000 Mbps, Cat6a or Cat7 is recommended.
• For 10,000 Mbps (10 Gbps) or higher, Cat8 is the only choice.

The calculator shows the maximum speed your cable can handle, which is the minimum of your internet speed and the cable’s rated capacity. For lengths over 55 meters, Cat6 drops to 1 Gbps, and Cat6a drops to 10 Gbps at 100 meters. The calculator uses the standard ratings for each category.

Worked Example

Using the default values: cable length = 20 meters, internet speed = 1,000 Mbps.

Step 1: Determine the maximum speed the cable can support. For a 20-meter Cat6 cable, the rated speed is 10 Gbps (10,000 Mbps), but your internet is only 1,000 Mbps, so the maximum speed is 1,000 Mbps.

Step 2: Find the recommended category. Since your speed is 1,000 Mbps, the calculator recommends Cat6.

Result: The maximum supported speed is 1,000 Mbps, and the recommended category is Cat6.

How Ethernet Cables Work

Ethernet cables carry data as electrical signals through twisted pairs of copper wires. The twisting cancels out electromagnetic interference from adjacent pairs and outside sources. Each category (Cat5e, Cat6, Cat6a, Cat7, Cat8) defines a specific level of performance, including bandwidth (MHz) and maximum data rate. Higher categories have tighter twists and better shielding, which allows them to transmit more data over longer distances.

The most common connector is RJ45, which is the same physical plug on all Ethernet cables. The difference lies in the internal wire gauge and shielding. For example, Cat6 uses 23 AWG wires, while Cat6a uses 23 AWG or thicker with more shielding. Cat7 and Cat8 use even more shielding, making them thicker and less flexible.

Choosing the Right Category

Here is a practical breakdown of each category:

• Cat5e: Supports up to 1 Gbps at 100 meters. Good for basic internet up to 1 Gbps. Cheapest option.
• Cat6: Supports up to 10 Gbps at 55 meters, and 1 Gbps at 100 meters. Ideal for most home networks with gigabit internet.
• Cat6a: Supports 10 Gbps at 100 meters. Thicker and more expensive, but better for long runs or high interference.
• Cat7: Supports 10 Gbps at 100 meters, with tighter shielding. Not standardized by TIA/EIA, but works with RJ45. Often overkill for home use.
• Cat8: Supports 25 or 40 Gbps at 30 meters. Designed for data centers. Not needed for home internet.

For most people, Cat6 is the sweet spot. If you have gigabit internet (1,000 Mbps), Cat6 will handle it fully. If you have faster than gigabit, Cat6a is a safer bet. If you only have 100 Mbps internet, Cat5e is fine and cheaper.

Length and Performance

Ethernet cable length affects signal quality. The maximum recommended length for a single copper cable is 100 meters (328 feet). Beyond that, the signal degrades and you may experience packet loss or slow speeds. Within 100 meters, the category determines the speed:

• Cat5e: 1 Gbps up to 100m
• Cat6: 10 Gbps up to 55m, then 1 Gbps up to 100m
• Cat6a: 10 Gbps up to 100m
• Cat7: 10 Gbps up to 100m
• Cat8: 25/40 Gbps up to 30m

If you need a cable longer than 100 meters, consider using a network switch to extend the run, or use fiber optic cable for longer distances. For home use, most runs are under 30 meters, so even Cat6 is overkill for speed but good for future-proofing.

Common Problems and Misconceptions

One common misconception is that a higher category cable will make your internet faster. That is false—your internet speed is limited by your ISP plan and your router. A Cat8 cable won’t give you more than 100 Mbps if that’s all you pay for. It only matters if you have a fast local network (e.g., transferring files between computers or using a NAS).

Another issue is buying flat or thin cables. They are easier to route but often have less shielding and can be more prone to interference. For permanent in-wall installation, use solid copper cables with proper shielding (STP) rather than stranded. Stranded cables are fine for short patch cables but lose signal over long runs.

Also, beware of counterfeit cables. Some cheap cables do not meet the category specs. Look for cables with a recognized certification mark (like UL) and check the wire gauge. A real Cat6 cable should have 23 AWG wires; if it’s 28 AWG, it’s likely not true Cat6.

Costs and Alternatives

Prices vary widely, but generally Cat5e is the cheapest, Cat6 is slightly more, and Cat6a/7/8 are significantly more expensive. For a 10-meter cable, you might pay $5 for Cat5e, $8 for Cat6, and $15 for Cat6a. The cost difference is small for short cables, but for long runs (50m+) it adds up.

Alternatives to Ethernet include Wi-Fi, powerline adapters, and MoCA (using coax TV cables). Wi-Fi is convenient but can be slower and less reliable, especially in crowded areas. Powerline adapters use your electrical wiring, but performance depends on house wiring. MoCA is great if you have coax outlets, offering near-gigabit speeds. For maximum reliability and speed, a wired Ethernet connection is still the best.

How to Buy and Install

When buying, determine the length you need (measure the path, not the straight line). Add a little extra for slack. Choose the category based on your internet speed and future plans. If you plan to upgrade to faster internet, buy a higher category now to avoid re-cabling later. For in-wall installation, buy bulk cable and terminate with RJ45 connectors yourself, or buy pre-made cables of the exact length.

Installation tips:

1. Keep cables away from power lines to avoid interference.
2. Use cable clips to secure the cable without crushing it.
3. Don’t bend the cable sharply; the minimum bend radius is usually 4 times the cable diameter.
4. For outdoor runs, use outdoor-rated cable (with a waterproof jacket).

Frequently Asked Questions

Does a higher category cable give me faster internet?

No. Your internet speed is capped by your ISP plan. A Cat8 cable will not make a 100 Mbps connection faster. It only matters for local network transfers or if you have a plan faster than the cable’s rating.

Can I use a Cat6 cable for a 10 Gbps connection?

Yes, but only up to 55 meters. For longer runs, you need Cat6a or higher to maintain 10 Gbps. For most home use, 10 Gbps is rare, so Cat6 is fine.

What is the maximum length of an Ethernet cable?

The official maximum is 100 meters (328 feet) for twisted-pair copper. Beyond that, signal degradation occurs. Use a switch or fiber optic for longer distances.

Is it worth buying Cat8 for home use?

Usually not. Cat8 is designed for data centers with 25/40 Gbps connections. For home, Cat6 or Cat6a is sufficient and much cheaper. Cat8 cables are also thicker and less flexible.

Should I buy shielded (STP) or unshielded (UTP) cable?

For most home environments, UTP is fine. Shielded cable (STP) is better if you run cables near power lines or in industrial areas with high interference. Shielded cable also requires proper grounding, which is tricky for home users.

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in t | Cable length | m | 20 | 1 | 100
in s | Internet speed | Mbps | 1000 | 1 | 10000
out maxspeed | Max supported speed | Mbps | min(s, 10000) | 0
out cat | Recommended category | - | 5 | 0