Bandwidth Delay Product Calculator
Find the bandwidth-delay product of a link.
The bandwidth-delay product is how much data can be 'in flight' on a link.
How the Math Works
The Bandwidth Delay Product (BDP) calculates the amount of data that can fill a network link during the time it takes for a signal to travel from sender to receiver and back. Using the formula BDP = bandwidth * RTT (Round Trip Time), you multiply the link's bandwidth in bits per second by the RTT in seconds. This yields the BDP value in bits, representing the total data 'in flight' across the link at any given moment.
Practical Applications
To apply this calculation, first determine your link's bandwidth in bits per second and measure or estimate the round-trip time in seconds. Multiply these two values together to get the BDP in bits. Network engineers use this value to size buffer windows appropriately, ensuring optimal throughput. For example, if you have a 100 Mbps link with a 50ms RTT, the BDP would be 100,000,000 * 0.05 = 5,000,000 bits (or 625,000 bytes) of data that can be in transit.
Day-to-Day Use
Understanding BDP helps explain why your internet connection might feel slow despite having high-speed service. When network buffers are too small for the BDP, data must wait for acknowledgments before sending more, creating idle time. This is why high-latency connections like satellite internet require larger buffers. By calculating BDP, you can better diagnose network performance issues and make informed decisions about technology choices that match your actual usage needs.
Worked example
100 Mbps with 40 ms RTT gives about 488 KB.
FAQ
Why does it matter?
If the TCP window is smaller than the BDP, you can't fill the pipe.