Enter the total operational time and the total number of failures into the calculator to determine the mean time between failures (MTBF).

MTBF Formula

The following formula is used to calculate the mean time between failures. 

MTBF = TOT / TF
  • Where MTBF is the mean time between failures
  • TOT is the total operational time (hours)
  • TF is the total number of failures

To calculate the mean time between failures, divide the total operational time by the total failures.

MTBF Definition

What is MTBF?

MTBF, short for mean time between failures, is a metric that describes the average time it takes to incur a failure on a piece of equipment.

The equipment can be manufacturing equipment that produces goods or something like air-conditioning.

Example Problem

How to calculate MTBF?

  1. First, determine the total hours of operation.

    For this example, we are looking at an air-conditioning unit that has been running for a year straight. This is equal to 8760 hours of operation.

  2. Next, determine the total number of failures during the time period.

    In this case, the air-conditioning failed a total of 5 times.

  3. Finally, calculate the MTBF.

    Using the formula above the mean time between failures is calculated to be:
    MTBF = TOT / TF
    MTBF = 8760/5
    MTBF = 1752 hours/failure