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File transfer time calculator with latency

Estimate file transfer time from file size, throughput, latency and an estimated number of round trips.

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đź”’ Inputs are processed locally in your browser.

How to use it

Estimate transfer time from file size and effective throughput, then add a simple latency component based on latency per round trip and an estimated round-trip count. It is a planning model, not a network simulator.

  1. Enter file size and its unit.
  2. Enter effective Mbps, latency in ms and a whole-number round-trip count.
  3. Compare base transfer time, latency component and estimated total.
Base time
file size Ă· effective throughput
Latency component
latency ms Ă— round trips
Round trips
Whole number of 0 or more
Model
Adds fixed waiting time per round trip

10 GB at 100 Mbps plus 30 ms Ă— 20 round trips adds 0.6 seconds of latency

The bandwidth-based transfer time is calculated first, then 30 ms Ă— 20 = 600 ms is added. For a large file, throughput usually dominates this simple fixed-latency term.

This does not simulate TCP congestion control, TLS handshakes, HTTP/2 or HTTP/3, or parallel transfers. It is only a “base transfer plus fixed round-trip waits” estimate.

Use effective throughput

A nominal 100 Mbps connection may deliver less for the actual transfer. Wi-Fi, VPNs and busy networks can make observed throughput much lower.

Treat the latency field as one round trip

If your measurement is one-way delay rather than RTT, convert or interpret it consistently before using it here.

Round trips are counted as whole waits

Use 0, 1, 2 and so on for the number of latency waits you want to add to the model.

Large files are often bandwidth-dominated

For multi-gigabyte transfers, hundreds of milliseconds of fixed waiting can be tiny compared with the total data-transfer time.

Many small requests need real measurement

Protocol behavior and concurrency matter much more for request-heavy workloads. Use browser/network traces or load testing for production performance work.

Related references: Digital storage units · SI prefixes & units