MTBF: how to calculate reliability in maintenance?

This article explains MTBF, a key indicator for assessing the reliability and availability of maintenance equipment. It is used to calculate the average operating time of an asset before it fails, with the aim of increasing productivity and efficiency by reducing the frequency of breakdowns.

In any company with a production facility, equipment failure is a major concern. Dealing with a fault can be annoying, costly and even dangerous for everyone, from the administrator to the operator. That’s why one of the main tasks of the maintenance department is to monitor equipment failures and reduce their frequency.

One of the best ways to check the effectiveness of maintenance tasks is to measure your company’s MTBF (Mean Time Between Failures). MTBF indicates the average frequency with which a failure occurs in a production system.

In addition to helping assess the frequency of failures, MTBF also helps predict the probability of a fault occurring during a given period. This information is crucial for meeting orders and estimating actual production capacity.

If you want to better manage your maintenance by controlling the reliability of your production equipment, you need to regularly measure the MTBF of your assets. In this article, we’ll show you how to calculate MTBF and why it’s so important.

What is MTBF, and how is it relevant to your business?

MTBF: definition and application

MTBF stands for Mean Time Between Failures. It’s a key parameter in determining the availability and reliability of your assets, as it indicates the average time a machine is up and running before it fails.

This performance indicator helps to assess the real availability of your production equipment, and is one of the most valuable indicators in any industry.

High MTBF is always desirable. The higher the MTBF, the shorter the average time a piece of equipment is out of service. Increasing MTBF is one of the most important challenges for a maintenance department, because a higher MTBF also means that the productivity and efficiency of each asset increases.

It’s important to note that MTBF only applies to repairable assets. It’s indeed impossible to calculate the mean time between failures if they can’t be repaired, as this would mean that the first failure of an asset would also be the last.

How do you calculate MTBF, and why is it important?

How do you calculate MTBF, and why is it important Calculating MTBF is simple: simply divide the total uptime of an asset by the number of failures that have occurred. We use the following formula:

  • MTBF = Total uptime / Number of failures

Typically, MTBF is measured in hours and failures. As such, the result will give you an MTBF in hours per incident, which corresponds to the number of hours you can expect a machine to run before it fails.

For example, if you have a machine that runs 12 hours a day and fails after five days of operation, our MTBF formula will be:


  • MTBF = (12 * 5) / 1 = 60

This means that the MTBF of this machine is 60 hours per failure, which tells us that we can expect the machine to run without incident for an average of 60 hours.

However, a single fault is not sufficient to calculate a meaningful average MTBF. It is necessary to wait for several faults to calculate an accurate MTBF. It’s important to note that the MTBF calculation differs when several faults occur, as the equipment downtime after each failure must be subtracted.

For example, supposing an asset ran for 200 hours last month and experienced 4 faults. Using our MTBF formula, we obtain:

  • MTBF = 200 / 4 = 50

This calculation, however, does not take into account the downtime after each fault. It is then necessary to subtract the total number of hours of downtime after each repair. For example, let’s calculate MTBF assuming that the repair time after each fault was 2 hours:

  • MTBF = 200 – (4 x 2) = 48

Thus, the MTBF of this equipment would be 48 hours per fault, indicating that we can expect the equipment to operate without incident on average for 48 hours. This remains however an average, and it is possible that the equipment may fail before reaching 48 hours of faultless operation, or even run longer without encountering any technical problems.


MTTR and MTBF: How to calculate total availability?

What is MTTR?

MTBF is just one part of the equation. As you probably know, it’s also important to take into account the downtime resulting from a fault. To this end, the Mean Time To Repair (MTTR) metric helps us understand how long it takes, on average, to restore an asset to normal operation after a fault. The higher the MTTR, the longer it takes to repair the asset after a fault.

To calculate the MTTR, we need to record the total downtime due to a fault and divide it by the number of repairs carried out. We can use the following formula:

  • MTTR = Total downtime / Number of repairs

For example, if an equipment was down for a total of 20 hours twice in a month, the MTTR would be:

  • MTTR = 20 / 2 = 10

This means that we can typically expect an asset to be operational again around 10 hours after a fault. Reducing the MTTR is one of the main duties of any maintenance department, to ensure that production equipment can return to normal operation as soon as possible after a fault.


How do you calculate total availability, and what does this mean for your company?

How do you calculate total availability, and what does this mean for your company MTTR is often used together with MTBF, as their combination helps us to determine the actual availability of production equipment. The MTBF indicates the frequency of faults, and the MTTR the average time required to repair them. Using these two metrics, we can plan how much machine maintenance is needed to reduce unplanned downtime.

You can use the following formula to calculate the total availability of your production equipment:

  • Total availability = MTBF / (MTBF + MTTR)

By increasing MTBF and reducing MTTR, you can maximize the productivity of your equipment and make the most of your assets.


Why are these indicators essential ?

Any company with production equipment needs to measure MTBF to be aware of the losses associated with faults and failures. Having good control over the MTBF of your production equipment will help you to:

  • Improve the operational efficiency of your production equipment.
  • Reduce maintenance costs.
  • Increase the reliability of your assets.
  • Extend the lifespan of your assets by reducing the occurrence of unplanned faults.
  • Identify potential risks in the production area.
  • Compare the performance of different assets.

With this information, you and your maintenance department can take more informed decisions about the use of your assets.


How can CMMS software help monitor these indicators?

The best way to record and manage the MTBF of your assets is with the help of a CMMS. CMMS software will help you manage your organization’s maintenance tasks, automating many processes that would be too time-consuming if carried out manually. By integrating key performance indicators (KPIs)  such as MTBF into your CMMS, you can bring the efficiency of your production team up to its optimum level.

For instance, a CMMS is essential for incorporating state-of-the-art maintenance practices such as planned maintenance. By integrating such a system, you can take advantage of regular asset downtime to improve production efficiency By tracking MTBF in your CMMS software, your maintenance department will be aware of how its efforts are helping to reduce the frequency of faults in your equipment.

Industrial Maintenance Industrial Maintenance Mob

MTBF is one of the most important metrics in maintenance. If your aim is to increase the efficiency of your assets and reduce the frequency of faults in your equipment, then keeping a record of your MTBF is crucial. Remember that to calculate MTBF, you need to divide the total uptime by the total number of faults that have occurred.

To reduce the frequency of incidents involving your assets and increase your MTBF, consider implementing a CMMS. DIMO Maint offers comprehensive maintenance solutions to maximize the efficiency of your operations. Contact us to speak with a qualified expert who will answer all your questions.

Contact us

Share this article
See also

Do you have a project, a question?

Do you have a project, a question? Hit us up and we’ll stay in touch

Scroll to Top