What is Bandwidth?

Bandwidth is the maximum data transfer rate of a network connection, measured in bits per second (bps). Common units include kilobits per second (Kbps), megabits per second (Mbps), and gigabits per second (Gbps). The theoretical bandwidth of a link is determined by its physical medium and encoding scheme, for example, a Cat6 ethernet cable has a nominal bandwidth of 1 Gbps up to 100 meters, as defined by the TIA/EIA-568-B standard.

In web hosting, the term is often used to refer to the total amount of data transferred to and from a server over a monthly billing cycle. This quantity is properly called "data transfer" or "traffic," but many hosting plans still label it as bandwidth. A shared hosting plan with "10 TB bandwidth" means the account can transfer up to 10 terabytes of data per month before incurring overage charges or service throttling. The distinction is important: a server connected via a 1 Gbps port could theoretically transfer more than 300 TB in a month, but the plan limits the actual usage to far less.

Bandwidth is a physical constraint on the maximum throughput of the underlying network path, from the server's network interface card through switches, routers, and the internet backbone. The effective throughput a user experiences is also limited by congestion, latency, and protocol overhead (TCP/IP headers, for example). In content delivery networks, bandwidth is a cost driver: CDN providers charge per GB transferred from edge nodes to end users. Proper capacity planning requires knowing both the peak bandwidth requirement (to size the port) and the 95th percentile or total transfer (to budget monthly costs).