MTBF means Mean Time Between Failures, and it is the average time elapsed between two failures in the same asset.

Along with MTTR (Mean Time to Repair), it’s one of the most important maintenance KPIs to determine availability and reliability. The higher the MTBF, the more reliable the asset.

In this article, we’ll explore how to calculate the MTBF, and why it’s decisive for a successful preventive maintenance plan. Ready?

How to calculate MTBF

To calculate MTBF, you need to divide the total operation time by the number of failures.

The total operation time is the difference between the total working time and the total breakdown time, so this is the MTBF formula:

MTBF formula

📌 In the MTBF formula:

  • total working time corresponds to the number of hours the machine would have been operating had it not failed; 
  • the total breakdown time is the unplanned downtime (thus excluding scheduled maintenance, i.e. inspections, periodic revisions or preventive replacements); 
  • the number of breakdowns equals the number of failures

MTBF Calculation Example

Let’s imagine that an asset which is expected to work for 24 hours a day has three outages. One lasts for an hour, another for 2 hours and the final breakdown lasts 30 minutes.

  • total working time = 24 hours 
  • total breakdown time = 3.5 hours (1 + 2 + 0.5)
  • number of breakdowns = 3 

📌 Then, as per the  MTBF formula, the Mean Time Between Failures calculation will be:

MTBF Calculation

Why is MTBF important?

MTBF is useful to estimate how likely an asset is to fail, and how often certain failures occur. This makes it extremely important for reliability engineering, although it’s also an indicator of the asset’s availability. 

While there are many more maintenance KPIs you should keep an eye out for, the MTBF is a guideline for preventive maintenance scheduling. Plus, if you make an accurate estimate, it will improve inventory and prevent stockouts. 

However, remember that any KPI is only as good as the data. To make sure you have accurate data from the equipment to calculate MTBF, you need the right platform

MTBF and MTTR: what’s the difference?

MTBF measures reliability, whereas MTTR is key to judge how efficient repairs are.

The Mean Time to Repair represents the average time it takes for an asset to be up and running again. Having a high MTTR means your assets and equipment are out of order for a long time after a breakdown. 

In other words, keeping a high MTBF ensures an asset is reliable. Maintaining a low MTTR ensures that downtime lasts as little as possible. Together, they allow managers to estimate how long a particular system is available or not. 

How to use MTTR and MTBF together

Analysing both MTBF and MTTR lets us predict productivity, plan scheduled downtime, and forecast the costs of preventive maintenance throughout the year. These insights aid facility managers in their decision-making process regarding which assets require the most maintenance, when, and which might need to be replaced. 

The aim is to decrease the number of breakdowns through intelligent preventive maintenance policies. A higher MTBF will make your company more credible and trustworthy, both internally and with your customers. Well done!

As for MTTR, try to cut it down. Your team must act quickly – the sooner you respond to failures, the faster they will be solved. But there’s a little more to it. On one hand, decreasing MTTR depends on efficient real-time maintenance management and clear work orders. 

On the other hand, you must understand why failures happen. Getting to the root cause of each failure is the only way to prevent it from happening again. Or, at least, to establish processes that make it less likely to occur again. Coupling swift action with root cause analysis will avoid lengthy breakdowns. 

💡 With a high MTBF and a low MTTR, your system will be working closer to full capacity. In this case, maintain best practices and never fail to invest in preventive maintenance! Here’s everything you need to know about preventive maintenance in 2023.

With Infraspeak, it’s easier to stay on top of both of these metrics and to improve your performance. Want to find out how? Talk to us!