Server Concurrency Calculator
Relate average throughput, response time and in-flight requests using Little’s Law.
Your result
EVERYDAYEnter your values and select calculate.
On this page How it works & practical examples
How to use the Server Concurrency Calculator
Use measurements from a stable system and a matching observation period. Mean response time includes the time relevant to your concurrency definition. The target row rearranges the same relationship for a chosen capacity utilization.
The calculation
Worked example
100 requests/second with a 200 ms mean response time corresponds to 20 average in-flight requests. A capacity of 50 then has 40% modeled utilization.
Assumptions and limits
Averages do not size peak concurrency or guarantee tail latency. Queue growth, burstiness, CPU, connection pools and downstream bottlenecks must be evaluated separately.
Common questions
Can I use the 99th-percentile latency?
Little’s Law uses a mean. Substituting a percentile changes the model’s interpretation.
Is the RPS row a load-test result?
No. It is an arithmetic estimate under the entered response-time assumption.