Throughput from Latency Calculator
A fast link does not guarantee fast transfers. TCP can only send one window of data before it must pause and wait for an acknowledgement to come back, so on a high-latency path even a large pipe sits idle between bursts. This calculator finds the throughput ceiling that latency imposes by dividing the TCP window size by the round-trip time. With a 65,536 byte window and a 50 millisecond round-trip, the most data you can move is 65,536 divided by 0.05, which is 1,310,720 bytes per second, about 10.49 megabits per second, no matter how fast the underlying link is rated. The page reports the ceiling in both bytes per second and megabits per second. The way to lift it is a larger window: TCP window scaling lets the window grow far beyond the old 64 kilobyte limit, which is essential on long fat networks that combine high bandwidth with high latency. Use it to explain why a transfer is slow, size a window for a satellite or transcontinental link, or sanity-check a tuning change. Every figure is computed deterministically from your two inputs, never estimated, with the method and a worked example shown below for verification.
Throughput is the window divided by the round-trip time: throughput = window / RTT. A 65,536 byte window over a 0.05 second round-trip caps throughput at 10.49 Mbps.
Throughput from latency formula
throughput (bytes/s) = window (bytes) / RTT (seconds)
bits per second = bytes per second x 8
Mbps = bits per second / 1,000,000
window = data that can be unacknowledged at once
The window is the most data TCP keeps in flight before it waits for an acknowledgement. Dividing it by the round-trip time gives the maximum sustained throughput.
Worked example
A connection has a 65,536 byte window and a 0.05 second round-trip time.
- Throughput = 65,536 / 0.05 = 1,310,720 bytes per second
- Bits per second = 1,310,720 x 8 = 10,485,760
- Mbps = 10,485,760 / 1,000,000 = 10.49
The ceiling is 10.49 Mbps. These are the calculator's default inputs, so the result above matches the widget exactly.
Throughput ceiling for a 64 KB window
Higher latency lowers the ceiling for a fixed window.
| Round-trip time | Max throughput |
|---|---|
| 10 ms | 52.43 Mbps |
| 50 ms | 10.49 Mbps |
| 100 ms | 5.24 Mbps |
| 250 ms | 2.10 Mbps |
Network performance and protocol concepts: US National Institute of Standards and Technology (NIST).
Throughput from latency calculator: frequently asked questions
How do you calculate throughput from latency?
Divide the TCP window size in bytes by the round-trip time in seconds. A 65,536 byte window over a 0.05 second round-trip gives 1,310,720 bytes per second, which is about 10.49 megabits per second. This is the most data that can be in flight before an acknowledgement returns.
Why does latency limit throughput?
TCP can only send up to one window of data before it must wait for an acknowledgement. On a high-latency link the wait is long, so even a fast pipe sits idle between bursts. The window divided by the round-trip time sets the ceiling, regardless of raw link speed.
How do I raise the limit?
Use a larger window. TCP window scaling lets the window grow well beyond the original 64 kilobyte limit, which is essential on long fat networks with high bandwidth and high latency. A bigger window keeps more data in flight and lifts the throughput ceiling.
Is RTT the same as latency?
Round-trip time is the time for a packet to reach the far end and the acknowledgement to return, so it is roughly twice the one-way latency. This calculator uses the round-trip time directly, because that is the interval TCP waits before it can send the next window.
Is the result computed automatically?
Yes. The page divides the window by the round-trip time deterministically and converts to megabits per second. No value is estimated or hard-coded, so changing either input updates the answer instantly.
Official sources
- Network performance and protocol concepts: US National Institute of Standards and Technology (NIST). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.