Grafana allows you to define and compute KPIs on multiple metrics. The metrics can be selected from a single or multiple queries with Grafana supported math functions (Sum, Min, Max, Avg, and so on).
Transformation (New feature in Grafana 7.x) can be leveraged to compute math operations on the results of multiple queries into a KPI. The result of the KPIs can also be used to compute another KPI (composite KPI) and visualized in Grafana widgets. The time interval selected for the reports also applies to the KPI computation, that is KPI can be recomputed for every changed results of metrics.