The longest ethernet cable you can use without losing noticeable speed depends on the cable category. For standard Cat5e, Cat6, and Cat6a cables, the maximum recommended length is 100 meters (328 feet), which includes 90 meters of solid cable plus 10 meters of patch cable. Beyond this distance, you may start to see signal degradation, slower speeds, or increased latency. If you need to extend past 100 meters, using network switches, repeaters, or fiber optic cables is recommended. Understanding the longest ethernet cable guidelines helps maintain a stable and reliable connection for both home and business networks.