Practical guide
TCP window and bandwidth-delay product reference
Calculate the TCP window needed for a bandwidth and RTT target, with decimal and binary unit conversions and practical limits.
Updated
Bandwidth-delay product (BDP) is the amount of unacknowledged data needed in flight to fill a path: bandwidth in bits/second × round-trip time in seconds. Divide by eight to express the result in bytes.
Worked calculation
For a 500 Mbps path with 40 ms round-trip time, BDP is 500,000,000 × 0.040 ÷ 8 = 2,500,000 bytes, or about 2.384 MiB. A single TCP flow generally needs at least that much usable receive window to fill the path under ideal conditions.
The bandwidth-delay product calculator converts the units. The transfer-time calculator estimates elapsed time for a payload after applying an efficiency factor.
Limits and common mistakes
BDP does not predict application throughput by itself. Congestion control, loss, sender and receiver buffers, parallel connections, server limits, and application behavior all matter. Use round-trip time rather than one-way latency, and label MB versus MiB when recording the result.