What is MTTF?

Mean Time To Failure — the lifespan of things you replace rather than repair.

MTTF (Mean Time To Failure) is the average operating life of a non-repairable item — a bearing, a filter, a light. Where MTBF measures repairable assets, MTTF measures consumables: how long until replacement.

MTTF drives stocking and replacement intervals: if a bearing's MTTF is 18 months, the storeroom needs one on the shelf before then — not after the failure.

• How it's used