MTTR Calculator

MTTR (mean time to restoration) is the expected time from a failure, or from its detection when the failure moment is unknown, until the asset is back in service. The figure is the average over an asset’s breakdowns. A lower figure means assets get back into service sooner.

Formula

MTTR = R ÷ N

• R is restoration hours: the hours from each breakdown until the asset is back in service, added together.
• N is the number of failures restored in the period.

R includes the hands-on work and the waiting for people, parts, approvals and access. Hands-on time alone is a different, smaller measure: mean repair time. It is not MTTR.

The MTBF and MTTR guide works through the method with a pump. Maintenance metrics and KPIs sets out when the restoration time starts.

FixAhead reports MTTR per asset. See the reporting features.

Source

IEC 60050-192, International Electrotechnical Vocabulary, Part 192: Dependability, on Electropedia. Entry 192-07-23 defines mean time to restoration as the expectation of the time to restoration, and deprecates “mean time to repair”. Entry 192-07-06 defines time to restoration from the instant of failure, or from its detection when that instant is unknown. Entries 192-07-19 and 192-07-21 define repair time and mean repair time, which exclude technical, administrative and logistic delays.

Worked example

Example only. The starting values are invented, and they are the same pump as the MTBF example.

• Failures restored: 5
• Restoration hours: 40, the pump’s unplanned downtime, which included 14 hours of waiting for parts

MTTR = 40 ÷ 5 = 8 hours

Of those 40 hours, 26 were hands-on repair. Hands-on time alone is mean repair time: 26 ÷ 5 = 5.2 hours. That is a different, smaller measure, not MTTR.