Reference desk
Availability Definitions
Availability figures cannot be compared until their downtime boundary is clear.
| Definition | Typical relationship | Includes |
|---|---|---|
| Inherent availability | MTBF ÷ (MTBF + MTTR) | Intrinsic failure and active corrective repair. |
| Operational availability | Operating ÷ total calendar state time | Repair plus logistics and administrative delay. |
| Production availability | Runtime ÷ planned production time | Site-defined production loss rules. |
Boundary discipline
Decide how planned maintenance, standby, no-demand time, partial capacity, and external constraints are treated. A precise formula with an unclear time model is not a reliable KPI.
Related tools
Inherent availability calculator, operational availability calculator, and availability guide.