Bandwidth Delay Product
Calculate how much data must be in flight to fill a network path.
Size the data needed in flight
Bandwidth-delay product is link rate multiplied by round-trip time. It represents the amount of unacknowledged data needed in flight to keep a path fully utilized under ideal conditions. This calculator converts megabits per second to bits per second, milliseconds to seconds, performs the multiplication, and reports bits, bytes, and binary mebibytes.
At the default 100 Mbps and 40 ms RTT, the path holds 4,000,000 bits or 500,000 bytes in flight, about 0.4768 MiB. A sender window substantially below that value cannot fill the ideal path even when there is no loss. The formula uses decimal Mbps, matching common network-rate notation.
BDP versus practical TCP throughput
BDP is not a guaranteed throughput result. Congestion control, receive windows, packet loss, competing traffic, protocol overhead, and application pacing all affect real transfers. The calculation runs privately in your browser and does not measure the route. Use an observed RTT and a realistic bottleneck rate, then compare the result with actual transport window and buffer settings.
Frequently Asked Questions
What does bandwidth-delay product represent?
It is the ideal amount of data in flight during one round trip at the selected link rate.
Does the Mbps input use decimal units?
Yes. One Mbps is treated as 1,000,000 bits per second.
Will a buffer equal to BDP guarantee full speed?
No. Loss, congestion control, overhead, receiver behavior, and application pacing can still limit throughput.
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