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Digital, Internet & Technology

Latency and Transfer Time Estimator

Estimate transfer time when latency and TCP window size limit throughput, with the bandwidth-delay product.

Your inputs

64 KiB is the limit without window scaling; modern systems usually scale far higher.

Results

Estimated transfer time

1 min 16 s

In seconds
76.34
Achievable throughput
10.486 Mbps
Limited by
TCP window (latency-bound)
Bandwidth-delay product (window needed for full speed)
610.4 KiB

≈Estimate based on the stated model and assumptions

Notes for this result

  • Simplified single-stream model: ignores TCP slow start, packet loss and congestion control.

What this calculator does

On long-distance links, a single TCP stream can be limited by round-trip time rather than bandwidth.

Formula and method

Window-limited throughput = window ÷ RTT; throughput = min(link, window ÷ RTT); BDP = bandwidth × RTT

Worked example

Calculated by this tool with its default inputs:

Inputs

  • Data size: 100 MB
  • Link bandwidth: 100 Mbps
  • Round-trip time (ping): 50 ms
  • TCP receive window: 64 KiB

Results

  • Estimated transfer time: 1 min 16 s
  • In seconds: 76.34
  • Achievable throughput: 10.486 Mbps
  • Limited by: TCP window (latency-bound)
  • Bandwidth-delay product (window needed for full speed): 610.4 KiB

How to read the results

If the window is smaller than the BDP, the link cannot be filled by one stream.

Assumptions and limitations

  • Simplified model; slow start, loss and congestion control are ignored.

Questions

How do I speed up a latency-bound transfer?

Larger TCP windows (window scaling), parallel streams or protocols designed for high latency.

Methodology and verification

Result type
Estimate based on the stated model and assumptions
Formula version
1.0
Automated verification
3 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
Editorial review
Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.

Privacy

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