Megabits (Mb) vs. Megabytes (MB): Why Transfer Speeds Confuse Users

Internet Service Providers (ISPs) advertise connection speeds in bits per second (such as 100 Mbps or 1 Gbps), whereas files, virtual disks, and database sizes are measured in bytes (MB, GB, TB).

Because there are 8 bits in 1 byte, a 100 Mbps broadband connection has a maximum theoretical throughput of:

100 Mbps ÷ 8 = 12.5 MB/s (Megabytes per second)

TCP/IP Protocol Overhead Factor

Data transmission across Ethernet or the Internet is packetized into IP datagrams (typically with an MTU of 1500 bytes). Each packet contains Ethernet headers (14 bytes), IPv4 headers (20 bytes), and TCP headers (20 bytes), plus bidirectional TCP ACK handshake packets. In practice, protocol headers and window congestion algorithms consume roughly 3% to 7% of total available bandwidth.