MTBF (Mean Time Between Failures)

The average operating time between one failure and the next for a repairable asset — a core reliability metric maintenance teams track to spot bad actors.

Definition

MTBF stands for Mean Time Between Failures. It is the average amount of operating time a repairable asset runs between one failure and the next. A higher MTBF means a more reliable asset. It is one of the most widely used reliability metrics in maintenance and is most useful for comparing assets, tracking whether reliability is improving, and prioritizing where to focus preventive effort.

MTBF formula

MTBF = total operating time ÷ number of failures over that period. For example, if a pump ran for 1,200 hours and failed 3 times, its MTBF is 400 hours. The number is only as good as the data behind it, which is why teams track failures in a CMMS — accurate failure counts and runtime are what make the metric trustworthy.

MTBF vs MTTR vs MTTF

MTBF measures reliability — how long an asset runs between failures. MTTR (Mean Time To Repair) measures maintainability — how long it takes to get it running again. The two together describe availability. MTTF (Mean Time To Failure) is used for non-repairable items that are replaced rather than fixed; MTBF is for repairable assets.

How to use MTBF in practice

Track MTBF per asset and watch the trend. A falling MTBF flags an asset that is degrading and may need a tighter preventive schedule, a rebuild, or replacement. Comparing MTBF across similar assets surfaces the bad actors that deserve attention first. Avoid over-reading a single number — MTBF is an average, so it is most meaningful as a trend over time on assets with enough failure history.

What is a good MTBF?

There is no universal target — it depends entirely on the asset and industry. MTBF is most useful as a trend (is it improving?) and as a way to compare similar assets, not as an absolute score.

What's the difference between MTBF and MTTR?

MTBF measures how long an asset runs between failures (reliability); MTTR measures how long it takes to repair after a failure (maintainability). Together they drive availability.