Every type of cable has a maximum distance. These distance limits can vary greatly from one type of cable to the next. Along with determining whether a cable will work, distance limits will also determine how well a cable works. Knowing the fundamentals behind cable distance limits is the first step in selecting the best cable for your needs.

Cables will always have some sort of “maximum signal” rating, depending on the type of the cable. For ethernet cables, it will be the maximum upload/download speed. For HDMI, it will be the maximum resolution of the video. And so on and so forth for other cables. Any type of “maximum” rating should be taken with a grain of salt.

Those ratings are the best possible rating the cable is capable of under theoretical, perfect conditions. For example, modern HDMI cables are all rated for 4k. But if the HDMI cable is running through a coupler, users will almost certainly not get 4k. Each time a signal passes through a connection, even just connecting a cable to something like a TV or computer, the signal quality degrades a little. Using devices like extenders and couplers will make the signal weaker; for example, coupling a 10’ cable to a 5’ cable will result in a weaker signal than just using a single 15’ cable.

Another key factor for signal quality is the distance of the cable. The further a signal has to travel, the more it will degrade by the time it gets from Point A to Point B. Going back to our HDMI example, a 15’ cord will give a clearer image than a 50’ cable. It is possible to get around this issue using an extender/booster. Some cables are also more subject to this issue than others, so doing a little research before running a particularly long cable never hurts.

When using cables with two different ends, the distance limit will be subject to whichever type of connector has the shorter maximum distance. For example, a standalone HDMI cable can go up to 65’ while a standard DisplayPort cable can go up to 15’. Therefore, an HDMI to DisplayPort cable will be stuck at 15’ for its maximum length.

Other factors such as electromagnetic interference or radio wave interference can also come into play. If the cable will be run near electrical cords or in an area near something like a radio tower, these issues can be mitigated by using shielded cables.

With this information in mind, remember that the rest of this article highlights the maximum distance a cable can run and still work. Some of these numbers are not officially acknowledged as industry standards, but real-world experience has taught us what to look for.

For information on audio/video cable distance limits, click here.

Data Cables

Ethernet - 100 meters (328 feet)

There are a few different versions of ethernet cable, but they all have a maximum distance of 100 meters (328 feet). It should be noted that Cat7 cable has harsher distance limits than Cat5e, Cat6, and Cat6a. Cat7 gets advertised for its 100 Gbps speed, but that will only work for distances up to 15 meters (slightly over 49 feet). Beyond that, it drops to the same 10 Gbps speed of Cat6 and Cat6a (although it still retains its superior 850 Mhz bandwidth).

USB - 15 feet (passive); 95 feet (passive + active extension); 200 feet (ethernet extension)

Passive (standard) USB cables have a maximum length of 15’. This limit can be overcome by using active USB extension cables. The active cables contain a microchip repeater that bypasses the normal 15’ limit of passive cables.

When daisy-chaining USB cables, there can be no more than 15’ of passive cable total. If you have a 10’ passive USB cable and try to attach a passive 10’ extension cord to it, the cable will not work. However, using a 5’ passive extension would work because the total amount of passive cable would only be 15’. These passive/active rules hold true for all the different types of USB cables.

An extender balun allows users to use an ethernet cable as an extension for USB. Different extenders have different maximum distance ratings but generally range somewhere from 150’ to 200’.

FireWire - 72 meters (236 feet)

FireWire has a maximum length of 72 meters (236 feet). Individual cables are only manufactured up to 4.5 meters (14.8 feet) long; going further than that means the cables must be daisy-chained together. A maximum of 16 cables can be used in a single chain.

Serial Cables - 15 meters (49 feet, standard); 60 meters (197 feet, with signal degradation)

Serial cables primarily consist of DB9, DB15, DB25, and DB37. They are also called RS-232, although that term usually refers to DB9 specifically. All of these have a maximum individual length of 15 meters (slightly over 49 feet). Extension cords can be used but past the 15-meter length, the signal will start to degrade. At 30 meters, the signal will have half the normal strength. At 60 meters, ¼ the normal strength. Going beyond 60 meters is not recommended.

Single-Mode Fiber Optic - No Practical Limit

Single-mode fiber can run for many kilometers before it stops working. Unless the cable is being lain long-distance for a telecom company, distance limits should never be an issue for single-mode fiber.

OM1 Multimode Fiber Optic - 300 meters

OM1 is the basic version of multi-mode cable, being able to maintain 1GB data speeds for up to 300 meters.

OM2 Multimode Fiber Optic - 600 meters

OM2 has the same data transmission speed as OM1 but doubles its maximum length for 600 meters total.

OM3 Multimode Fiber Optic - 300 meters

OM3 has the same 300-meter distance limit as OM1 but is also capable of transmitting data ten times faster at 10GB.

OM4 Multimode Fiber Optic - 550 meters

OM4 carries a 10GB up to 550 meters, providing a distance upgrade to OM3 (similar to how OM2 has the same speed but a greater maximum length than OM1).