What Is Mean Time to Repair (MTTR)?

Let’s be real: Maintenance teams can be spread thin. So, wouldn’t it be great if there was a way to not only calculate how long it takes to repair a piece of equipment but to also help determine if that asset has reached its full lifecycle and whether or not it should be replaced?

Enter Mean Time to Repair (MTTR) — a metric that measures the average amount of time it takes to repair an asset after it fails.

What Do We Mean by Mean Time to Repair? 

MTTR is a calculation of the average time it takes an individual or team to diagnose the root cause of an asset issue, repair it, complete its maintenance and get it back to normal operation. 

Businesses use this metric to evaluate failing systems or components. It allows them to improve operational efficiency and minimize asset downtime by reducing the number of failures within a specific period. Units of time and repair incidents are used to calculate these metrics. 

MTTR vs. MTBF vs. MTTF 

Before we get to the MTTR calculations, it’s important to understand the other failure metrics that maintenance teams can track. While MTTR is a system failure metric that measures average repair time, Mean Time Between Failure (MTBF) is the average time between breakdowns of a piece of equipment or system; this is the time in which it remains operational. The average MTBF is the total time of an asset’s operation divided by the number of failures that occur during that time. 

Another similar metric — Mean Time to Failure (MTTF) — measures the average life expectancy of a piece of equipment or system, measured by its initial failure under normal conditions. A higher MTTF (i.e., more time between failures) means the asset is more reliable, while a lower MTTF means it’s more likely to break down. 

The differences between MTTR, MTBF and MTTF lie in the asset used in the metric. MTTR and MTBF metrics typically use repairable assets in their calculations — when assets do break down, easy and inexpensive repairs are possible. MTTF uses only non-repairable assets in its equation. 

How Do You Calculate Mean Time to Repair (MTTR)? 

MTTR is calculated by dividing the total repair time for any failure by the number of repairs during a given period. When an organization keeps track of asset maintenance, it makes it that much easier to track MTTR for these assets. 

To calculate MTTR, you’ll first determine the total amount of repair time for a given asset. For example, a conveyor belt resulted in failures that required a total of three hours of repair time over one month before it was fixed. 

Next, you’ll add the total number of repairs during that time — in this example, we’ll use two repairs. Three hours of total repair time divided by two total repairs is 1.5 hours of MTTR. 

With the information at hand, you can now evaluate the result and set a benchmark to improve performance, productivity and efficiency and potentially reduce the time it takes to identify, fix and test repairs overall. Just remember that calculations using this MTTR formula will differ based on the asset, its age and how necessary it is to an organization’s production.

Benefits of MTTR 

MTTR influences many aspects of an organization’s efficiency and operational management systems. It provides valuable information to businesses so they can not only make informed decisions about an asset but also reap benefits in other areas. The most significant benefits of MTTR include:

• Reducing asset downtime: Faster repairs reduce asset downtime, which, in turn, boosts the productivity and efficiency of an organization. 
• Improving an asset’s reliability: A consistently functional piece of equipment or system improves the business’ service delivery and customer satisfaction overall, as uptime is increased and disruptions are minimized.
• Helping determine if assets need to be repaired or replaced: By identifying trends in MTTR, an organization can develop a maintenance management schedule to keep the asset in good working condition for the duration of its lifetime. 
• Giving insight into team performance: MTTR also gives organizations an accurate analysis of how well teams respond to and repair assets. With less time required for repairs and fewer repairs on one asset, a team can handle more tasks within a specific timeframe and attend to other challenges that may creep up.

The lower the MTTR, the greater the potential cost savings for an organization are, as emergency repairs to assets are reduced, lost revenue to downtime is diminished and the need for additional employees to manage issues is lessened.

Example of Using MTTR 

Let’s look at how MTTR is used with another example. A manufacturing plant that operates multiple production lines loses one of its most critical machines when it breaks down and halts production. To calculate MTTR in this scenario: 

• Define the start time: This is the moment the machine breaks down and stops functioning. If the machine breaks down at 9 a.m., that is the start time. 
• Define the end time: This is the time when the machine is, once again, fully operational and production resumes. If the machine is functional by 1 p.m., that is the end time. 
• Calculate MTTR: MTTR is the total time taken to repair the machine divided by the number of breakdowns within a specific period. For this example, the machine breaks down at 9 a.m. and resumes function at 1 p.m., for a total downtime of four hours. One breakdown occurred during that time. Divide a total downtime of four hours by one repair, and the MTTR is four hours. If the same asset has multiple breakdowns over a month, you would add up all the times the asset was down and divide the total number of breakdowns to get an average repair time. 

With the information at hand, the business can evaluate the result to gauge the efficiency of its repair processes or the health of the asset being repaired. A high MTTR may indicate the need for more team training, or it may indicate that the asset is at the end of its lifecycle. A lower MTTR shows that there is a healthy process in asset maintenance, repair training and recovery time.

Challenges in Measuring MTTR 

MTTR metric calculations should be straightforward; however, several factors may complicate attempts to quantify them. For example, the availability of data may be a concern if a business does not have a method for consistently collecting its data. Identifying repair time may be another issue. How is it defined? Does it begin when detection of the problem occurs or when the repair starts?

The nature of the repair and who does it will also bear an influence on repair time, as will operating conditions like location and working environment. If the repair is difficult, the technician is less skilled or the asset is in a remote location and the repair is taking place under hazardous conditions, the MTTR may be higher than it would normally be. Getting technicians, teams and departments on the same page regarding skillset and procedures is essential to achieving accurate calculations as well as optimal efficiency. 

Missing or incomplete records of previous repairs can also skew MTTR calculations. If there is more than one failure at a time on an asset, it may be hard to distinguish between related repair duties and assign start and end times necessary for the calculation. 

Other Types of MTTR 

While Mean Time to Repair is a common term in the maintenance world, the MTTR acronym actually has a few meanings that differ slightly:

• Mean Time to Resolve: This measures the mean (or average) time it takes to resolve an issue. It starts from the moment the issue was reported to the time the problem is fully resolved and the asset is operational. It is calculated by the total time it takes for an incident’s resolution divided by the number of incidents. 
• Mean Time to Respond: This metric calculates the average time it takes to respond to the failure of a particular product or system. It starts at the moment of an issue’s detection and ends when normal operations of an asset resume. Mean Time to Respond doesn’t include the time the issue goes undetected or lag time in the asset’s alert system. It is calculated by adding the full incident response time from detection to when the asset is fully functional divided by the total number of incidents in a specific time period. 
• Mean Time to Recovery: Also sometimes referred to as “Mean Time to Restore,” Mean Time to Recovery is essentially measures an asset’s full outage time as well as time spent resolving the problem. It is calculated by adding total downtime during a specific period and dividing it by the total number of incidents during that time. 

How to Improve Mean Time to Repair 

There are several ways to improve MTTR processes and calculations, all which will lessen downtime and promote efficient operations overall. These include: 

• Establishing standardized repair procedures: Implementing standard procedures with all team members will increase the likelihood of repairs going smoothly and more consistently. This can be accomplished by using checklists in work orders, documenting procedures as repairs are made and providing training to technicians and team members. This may include response simulations to equipment or system issues that may arise. Establishing procedures will prepare teams for potential problems and allow them to readily identify areas for improvement. 
• Implementing a CMMS: A computerized maintenance management system software (CMMS software) like Coast allows teams to track work orders, view parts inventory and keep track of preventive maintenance schedules. Technicians with immediate access to CMMS data can quickly act on a repair or maintenance to get the asset up and running sooner. 
• Improving availability and accessibility of parts: Having a better parts inventory system for an asset is a preventive measure that will improve MTTR greatly. The more parts available to technicians and teams, the easier and quicker it will be to make a repair or perform maintenance duties to keep the asset in operation. Supplier relationships are important to this process — it’s best to work with multiple vendors and not be dependent on just one to ensure parts are available to order at all times. 
• Performing preventive maintenance: By being proactive about performing preventive maintenance and monitoring assets to detect smaller issues as they occur will help avoid larger breakdowns that stop production in the future. This can include automating inventory and maintenance systems to help keep production-critical assets functioning normally.