Throughput Calculator
Measure effective network throughput after accounting for overhead and loss.
About Throughput Calculator
TCP throughput is fundamentally limited by the sender's window size (how much unacknowledged data can be in flight) divided by the round-trip time, since the sender must wait for acknowledgments before the window slides forward. This relationship — throughput = window size / RTT — is known as the bandwidth-delay product relationship, and it explains why high-latency links need larger TCP windows (window scaling) to fully utilize available bandwidth.
Formula
Maximum throughput
throughput = window_size / RTT
- W
- TCP window size in bytes
- RTT
- Round-trip time in seconds
Worked example
With the default values below, Throughput Calculator returns Max Throughput of 10.486. Change any input above and every figure here is recalculated in your browser.
Inputs used
- TCP Window Sizeminimum 1 bytes
- 65,536 bytes
- Round-Trip Time (RTT)minimum 0.01 ms
- 50 ms
Results
- Max Throughput
- 10.486 Mbps
- Throughput
- 1,310,720 bytes/s
- Throughput
- 10,485,760 bps
Step by step
- 1Values used
- 2Maximum throughput
- 3Max Throughput= 10.486 Mbps
- 4Throughput= 1,310,720 bytes/s
- 5Throughput= 10,485,760 bps
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why does RTT limit throughput even with plenty of bandwidth?
TCP can only have one window's worth of data 'in flight' unacknowledged at a time. If the RTT is high, the sender spends more time waiting for acknowledgments, so even a fast link is bottlenecked unless the window is large enough to keep the pipe full.
How do I increase throughput on a high-latency link?
Increase the TCP window size (via window scaling, RFC 1323) so more data can be in flight before an acknowledgment is required, or use multiple parallel TCP connections to work around a single connection's window limit.
What is the bandwidth-delay product?
It's the same formula rearranged: bandwidth × delay = the amount of data that can be 'in the pipe' at any moment. To saturate a given bandwidth over a given RTT, your window size needs to be at least that bandwidth-delay product.
Does this account for packet loss?
No — this calculates the theoretical maximum assuming no loss. Actual throughput on a lossy link is typically much lower because TCP congestion control shrinks the window in response to lost packets.