MTTF Calculator — Mean Time To Failure

MTTF = total operating hours ÷ number of units that failed. It’s the expected life of a non-repairable part — a bearing, a seal, a fuse — before it fails and is replaced. Higher MTTF is better.

MTTF is for parts you replace, not repair. For machines that go back into service after a fix, use MTBF instead.

MTTF is most useful for spares planning: it tells you roughly how often a part will need replacing, so you can set PM intervals and stock levels before the failure, not after it.

This calculator works from hours and unit counts you enter by hand for one part type. Logging part replacements against work orders in MachDatum CMMS keeps the history you need to work it out.