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Bandwidth–RTT Data in Flight

Multiply link throughput by round-trip time to calculate a bandwidth-delay product in bits or bytes.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

A 100 Mb/s rate and 50 ms round-trip time give a bandwidth-delay product of 5 Mb, equal to 625,000 bytes.

Bandwidth-delay product = throughput per second × round-trip seconds

Worked example

Enter these known values and leave the other values blank.

Target throughput
100 Mbit /s
Round-trip time (RTT)
50 ms
Bandwidth-delay product
5 Mbit

Assumptions and limitations

  • Use round-trip delay, not a one-way propagation delay. The model assumes a steady rate and a representative RTT.
  • The result is an amount of data, not a transfer speed. Bits and bytes differ by a factor of eight; the selectable prefixes here are decimal.
  • BDP is useful when reasoning about data in flight. It is not a complete recommendation for a TCP window or router buffer: protocol behavior, congestion, loss, concurrent flows and system limits also matter.

Common questions

Should I enter ping time or half of it?

Use the measured round-trip time in this formula. Do not halve it merely to estimate one-way delay.

Why is the answer smaller when displayed in megabytes?

Each byte contains eight bits. Five megabits is 0.625 megabytes, with decimal prefixes.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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