How does AppDynamics calculate Average Response Time (ART)?

Average Response Time is the mean elapsed time, in milliseconds, from when a Business Transaction's entry point begins executing to when it returns a response, averaged across all the calls to that Business Transaction within the selected time window.

Every individual execution the agent observes contributes its own end-to-end duration — entry point through every downstream call it made and back — and those durations are aggregated at the granularity AppDynamics stores metrics at (one-minute buckets by default) before being averaged over whatever wider window you're viewing, such as the last hour or last day.

Because it's a mean, ART can hide a bimodal problem — for instance, 95% of calls finishing fast and 5% finishing extremely slow can still produce an ART that looks only mildly elevated, which is exactly why percentile-based views and individual transaction snapshots matter alongside the ART number rather than relying on the average alone.