Bandwidth Delay Product Calculator
The bandwidth delay product is one of the most useful numbers in network tuning. It tells you how much data can occupy a link end to end, which is exactly the amount a sender must keep unacknowledged to use the full line rate. When the TCP receive window is smaller than this product, throughput stalls and the connection cannot fill the pipe. Enter your link bandwidth in megabits per second and the measured round-trip time in milliseconds, and this calculator returns the bandwidth delay product in bits, bytes, and kilobytes so you can size socket buffers and window settings correctly.
Bandwidth delay product formula
Bandwidth (bits/s) = Mbps * 1,000,000
RTT (seconds) = ms / 1,000
BDP (bits) = bandwidth bits/s * RTT seconds
BDP (bytes) = BDP bits / 8
BDP (kilobytes) = BDP bytes / 1,024
BDP (megabytes) = BDP bytes / 1,048,576
The product of bandwidth and delay gives the link capacity in bits. Dividing by 8 converts to bytes, the unit used when configuring TCP window and socket buffer sizes. Kilobytes and megabytes use the binary 1,024 convention common in operating system buffer settings.
Network tuning context
- The BDP is the minimum TCP window needed to keep a link fully utilised; smaller windows leave the link idle while waiting for acknowledgements.
- Bandwidth is conventionally quoted in decimal megabits (1 Mbps = 1,000,000 bits/s), while buffer sizes are conventionally binary (1 KB = 1,024 bytes).
- High-latency links such as satellite connections need large windows because their RTT is large even at moderate bandwidth.
- The TCP window scale option (RFC 7323) is required when the BDP exceeds 65,535 bytes, the maximum unscaled window.
- RTT can be measured with the ping tool; use a value representative of your typical path, not the minimum.
Bandwidth delay product: frequently asked questions
What is the bandwidth delay product?
The bandwidth delay product (BDP) is the amount of data that can be in transit on a network link at any one time. It equals the link bandwidth multiplied by the round-trip time (RTT). The result, expressed in bits or bytes, is the maximum amount of unacknowledged data a sender must keep in flight to fully use the link.
Why does the BDP matter for TCP throughput?
TCP can only send up to one receive-window worth of data before it must wait for an acknowledgement. If the receive window is smaller than the BDP, the link sits idle while the sender waits, capping throughput well below the line rate. Sizing the window to at least the BDP keeps the pipe full and lets TCP reach the available bandwidth.
How do I convert the BDP from bits to bytes?
Network bandwidth is quoted in bits per second, so the raw BDP is in bits. Divide by 8 to convert bits to bytes, because there are 8 bits in 1 byte. TCP window settings are configured in bytes, so the byte value is the figure you use when tuning a socket buffer or system parameter.
What units should I enter for bandwidth and RTT?
Enter bandwidth in megabits per second (Mbps) and round-trip time in milliseconds (ms), which are the units most network tools report. The calculator converts internally: 1 Mbps is 1,000,000 bits per second and 1 ms is 0.001 seconds, so the product gives bits, which it then converts to bytes and kilobytes.
Is the BDP the same as latency?
No. Latency (the RTT) is a time, measured in milliseconds. The BDP is a quantity of data, measured in bytes, that depends on both the latency and the bandwidth. A high-latency satellite link and a low-latency fibre link can have the same BDP if their bandwidths differ in proportion to their RTTs.
Official sources
- IETF RFC 7323: TCP Extensions for High Performance.
- IETF RFC 1323: TCP Extensions for High Performance (original).
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.