Mean Time To Failure (MTTF) represents the span of time that a product or equipment is expected to function until it gets breakdown and needs to be replaced. MTTF indicates the life time of a Product or equipment.

It is used to measure reliability of non-repairable products and Equipment.

Mean Time To Failure MTTF

Mean Time To Failure is calculated by looking at a entire number of the products or equipment of the same kind over an extended period of time and tracking the duration of time they last before they fail or breakdown.

Calculating MTTF

MTTF is calculated as the total time of operation, divided by the total number of equipment being tracked.

MTTF = Total Operating Time / Total Number of Equipment


Let’s assume we tested 3 pulley belts. The first one failed after 5000 hours, the second one failed after 6000 hours, and the third belt failed after 7000 hours of use.

Here the MTTF will be:

Total operating time = 5000 + 6000 + 7000 Hours

= 18000 Hours

Total number of equipment = 3

MTTF = Total Operating Time / Total Number of Equipment

MTTF = 18000 / 3

MTTF = 6000 hours

From the above example we understand that the pulley belts of the particular type or model is estimated to perform for 600 hours after which it needs replacement.

Higher the MTTF more reliable the product is and lesser the MTTF less reliable the product is.

This information will help the maintenance team to take decision on the reliability of the belt that they use and plan for the replacement or other things.

To improve the MTTF for the product is by ensuring the proper use of the equipment as directed by the supplier or to look at a better quality of the product available in the market.

We believe this blog would have helped you have crisp and clear information about what is Mean Time To Failure (MTTF), calculating MTTF and the inference of the calculated data. Please do leave your comments and questions which will help us know the feedback.

You can read about Mean Time To Repair – MTTR and also on Mean Time Between Failure (MTBF) to relate between the MTBF, MTTR and MTTF for better understanding.

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