What is the hazard rate?

The hazard rate λ, also known as the failure rate, is an important parameter for measuring the reliability of objects. The hazard rate indicates the probability with which an object fails in a certain period of time or how many objects fail on average in a certain period of time.

How to calculate the hazard rate?

To calculate the hazard rate at a given time, divide the number of failed objects (in a time interval), by the number of objects that were functional at the beginning of the time interval.


1,000 machines are put into operation at the beginning of a day. At the end of the day, 996 machines are still in operation. Thus, 4 machines have failed.

4/1,000 = 0.015 resp. 0.4%


4/1,000/24 = 166.7 failures per million hours

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