Work out load test concurrency instantly with clear inputs, formula shown and shareable results.
Virtual users and requests per second are not the same thing. Each virtual user completes one request per cycle of response time plus think time, so achieving 1,500 requests per second with a 3.2-second cycle needs about 4,800 virtual users. Concurrency at the server is much lower, because think time is spent idle — confusing the two is the most common load-test sizing error.
Virtual user count
cycle = response time + think time; virtual users = target RPS x cycle; server concurrency = target RPS x response time
Because it models real user pacing and connection reuse. Removing it produces a hammering pattern that stresses different bottlenecks than production traffic does.
Then the test measures the generator, not the service. Watch generator CPU and socket limits, and distribute across enough hosts that they stay well below saturation.