Mean Time To Resolution

Mean Time To Resolution (MTTR) is one of the "DORA metrics" and a critical key performance indicator (KPI) in Incident Management. It measures the average time elapsed from the moment an incident is **detected** to the moment it is **fully resolved** (i.e., the service is restored and functioning normally for users). ### Why MTTR is the "North Star" Metric MTTR is often considered the single most important metric for SRE teams because it directly correlates with customer downtime. Unlike Mean Time Between Failures (MTBF), which measures reliability, MTTR measures **resilience**: how quickly your system bounces back when (not if) it fails. > "You cannot prevent every failure, but you can control how fast you recover." *Note: In common industry usage, "Average" and "Mean" are used interchangeably. We use "Average" here for clarity, though "Mean" is the precise statistical term.* ### How to Calculate MTTR To calculate MTTR, divide the **total downtime** of all incidents during a specific period by the **total number of incidents** in that same period. **The Formula:** ```math MTTR = (Sum of all incident durations) / (Total number of incidents) ``` **Example Calculation:** If your team faced 4 incidents in Q1 with durations of 30m, 60m, 15m, and 15m: * Total Downtime = 30 + 60 + 15 + 15 = 120 minutes * Total Incidents = 4 * **MTTR = 120 / 4 = 30 minutes** ### MTTR vs. Other Metrics * **MTTD (Detect)**: Time to realize there is a problem. * **MTTA (Acknowledge)**: Time for a human to start working. * **MTTR (Resolve)**: The total time until the fix is live.