The maximum length for a LAN cable, also known as an Ethernet cable, is 328 feet (100 meters), including up to 16 feet (5 meters) of patch cable on each end. This limit is based on standards from the Telecommunications Industry Association (TIA) and Electronic Industries Alliance (EIA). Beyond this length, the signal can degrade, which can reduce the speed and reliability of the connection. However, it's possible to exceed the manufacturer's specifications and still maintain network connectivity, though the chances of issues increase. Using a high-quality shielded cable can help offset the length limit and maintain a good connection.
The length limit for a permanent link, which is a solid copper structure cable that runs inside walls, below floors, and in basements, is 295 feet at 68 degrees F. The length can get shorter as the temperature rises.
Different LAN cables have different maximum network speeds, but medium runs (1 to 10 meters) are suitable for most home and office setups, while long runs (10 to 100 meters) are needed for larger spaces.
What happens if your Ethernet cable is too long?
While you can buy pre-made Ethernet cables of the right length, you can also buy Ethernet cables in bulk and make your own cables of theoretically any length. You may even be able to successfully use Ethernet cables longer than 100 meters; especially if you use high-quality cables with solid shielding and construction materials. However, you will find that the performance of the cable will degrade, resulting in lower data transfer rates and reduced signal stability. This can cause stuttering in streaming videos, lags in gaming, or even data corruption when downloading.
If you are using a specific category of Ethernet cable to achieve a specific desired network speed, it is also important to consider how long the Ethernet cable can stretch across this network, as some Ethernet cables can only run at their rated speeds up to a certain length. For example, a Cat 6 Ethernet cable can run at speeds of up to 10 Gbps up to 55 meters (180 feet), but once you exceed that threshold, the speed is limited to only 1 Gbps and will continue to remain that way until the maximum length of 100 meters.
Cat 6A, on the other hand, is capable of handling 10 Gbps over distances of up to 100 meters, while Cat 8 cables can handle up to 40 Gbps over the same length.