Cloud & Networking

Bandwidth-Delay Product Calculator

Find how much data is in flight on a link, and the TCP window needed to fill it.

By TheCalcTools Updated Formula checked and tested

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BDP (bytes)
BDP (bytes)
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BDP (MB)
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BDP (MiB)
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Bandwidth-Delay Product Calculator by TheCalcTools

How the Bandwidth-Delay Product Calculator works

Enter the link speed and the round-trip time.

The product of the two is the number of bits that can be in transit at once.

A TCP receive window at least that big is needed to keep the link full.

The formula

BDP = bandwidth (bits/s) × RTT (s) ÷ 8

Worked example

Using the default values shown in the calculator:

Bandwidth (Mbps)1000
Round-trip time (ms)50
  1. 1,000 Mbps × 0.050 s = 50,000,000 bits.
  2. Divided by 8 that is 6,250,000 bytes.
  3. About 6.250 MB, or 5.960 MiB, must be in flight to fill the link.

Result:

BDP (bytes)6,250,000
BDP (MB)6.250
BDP (MiB)5.960

Frequently asked questions

What happens if the TCP window is smaller than the BDP?

The sender stops and waits for acknowledgements, so throughput is capped at window ÷ RTT, below the link speed.

What is a long fat network?

A link with a large BDP, such as a high-bandwidth intercontinental path. It needs window scaling (RFC 7323) to perform well.

Sources and further reading

TCP Throughput CalculatorSee what limits a TCP connection: the window, or packet loss Network Latency Calculator (Fibre Distance)How much latency does distance add to a network path? Page Load Time Calculator (Size, Bandwidth, Latency)Enter the page weight, connection speed and latency

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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.