OEE Calculator – Discover your hidden factory

How Does the OEE Calculator Work?

The first part, “Calculate OEE”, in the OEE calculator delivers the value using minimum information:

1. Your scheduled working time (per month)
2. The number of good products (per month)
3. And your theoretical maximum production speed

To calculate your OEE in a simple way, this is all you need.

The second part, “Calculate OEE components”, gives you the values of Availability, Performance, and Quality components of OEE. This part needs additional information:

1. Sum of all machine stops, per day (or downtime). We then multiply this value with the number of working days per month.
2. The number of scrapped products or products needing rework (per month)

You may notice that if you change the second part in the calculator, the OEE value does not change, only the OEE components change.

Below, we have an introduction to how OEE is calculated, common mistakes made, and how to troubleshoot the OEE calculator.

The Logic Behind the OEE Calculator

Overall Equipment Effectiveness (OEE) shows how many products you actually produce, as a percentage of how many you could produce if the equipment was running at theoretical maximum speed with zero scrap and rework.

If we replace the words in this sentence with numbers:

OEE

Number of good products you produce

Number of products you could produce theoretically

The “number of products you could produce theoretically” refers to your theoretical maximum for the given time period:

You get the theoretical maximum () if you multiply the scheduled working time () of your machines with your maximum production speed ()

OEE

Number of good products you produce

Number of products you could produce theoretically

Number of products you produce

Scheduled working time x Maximum production speed

OEE

Number of good products you produce

Number of products you could produce theoretically

Number of products you produce

x

How to find your maximum production speed?

Sometimes the manufacturer of the machine specifies it (alternative terms – “nameplate”, or “ideal cycle time”). If not, you can identify the fastest recorded time by looking at historical performance and then calculate how many products you would make if your machines were constantly running at that speed.

Why is calculating just OEE (without knowing its components) useful?

Being able to calculate OEE with minimum information means that you can find it out as early as possible, without knowing your downtime and quantities of scrapped products. This helps you set a baseline that you can use in the future to evaluate your trends and the impact of process improvements. It also allows you to benchmark within the company and against industry averages.

From our experience, most of Evocon’s clients initially overestimate their OEE values compared to the actual numbers measured with an automated system. This will often come as a surprise but also highlight great opportunities for improvement.

Here’s a quick snapshot of OEE and its components’ formulas:

OEE = Availability x Performance x Quality

Availability = Run Time / Planned Production Time

Performance = (Ideal Cycle Time x Total Count) / Run Time

Quality = Good Count / Total Count

For a more detailed look at the calculation, read our guide: How to Calculate OEE – Formulas & Examples

Breaking Down the 3 Components of OEE

Now that you know how to calculate OEE in a simple way and set your baseline using our OEE calculator, you can set your target OEE and focus on improving your OEE. This is where the OEE components come into play:

• Availability
• Performance
• Quality

The reason to calculate the components and not just OEE alone is that they show you how to improve OEE and eliminate the Six Big Losses in Manufacturing. For each of these components, there are different strategies and methods of improvement.

Watch the video below to learn more about OEE and how to calculate it:

What is Availability?

Availability is essentially the time that your machines are actually working, as a percentage of scheduled working time.

This OEE component is especially useful in the beginning when you just start improving your OEE. Availability improvements are the “low-hanging fruit”. Downtime is fairly straightforward to estimate, and solutions often become obvious as soon as you start recording reasons for machine stoppages.

What is Performance?

Performance (or production speed) shows how fast your machines or production lines are running.

100% Performance means that they are running at their maximum speed. 50% means that they are running at half the speed and producing only half the number of products.

So, to calculate Performance, you need to find out how many products you produce, and how it compares to the number of products that you could produce at maximum speed during your actual (not all scheduled, but actual) working time.

Turning your attention to Performance opens up new possibilities for improvement because Performance issues are often overlooked and underestimated by management. They are also difficult to detect if you collect production data manually. Therefore, implementing an OEE system gives you significant advantages.

What is Quality?

Quality shows the proportion of good products among all products.

Defects are expensive since you waste the materials and lose all the production time spent making products that are scrapped in the end. In the case of rework, the extra time spent is wasted, and in most cases, rework creates extra losses due to the interruption of the standard workflow.

How Do All OEE Components Work Together?

OEE components are often visualized as each of them being a percentage of the other one. Below is a visualization of this concept:

As you can see above, if you multiply all OEE components with each other, you will get the OEE value. Accordingly, if you know your OEE value and only two OEE components, you can find out the missing OEE component.

Why Automate Your OEE Calculation?

Using our OEE calculator online, you can estimate your current level, but we still recommend an automated solution and creating your own OEE Dashboard. Below, we discuss manual production monitoring and the benefits of an automated production monitoring system.

Manual production monitoring

Manual production monitoring means that you use a stopwatch to track how long your machines work or sit idle. You could write down the times and notes with a pen on paper, or you could enter it in an Excel spreadsheet. Either way, it means that a human measures the work of a machine.

Manual production monitoring has a long history in manufacturing and provides significant benefits. It is quick and easy to implement and allows you to capture the most significant machine stops.

If the person who monitors production notes down the reasons for those machine stops, a simple analysis of data, later on, reveals the most popular downtime reasons. By eliminating these downtime reasons, you can improve your Availability.

Automated production monitoring

However, manual production monitoring has a few problems. By installing an automated production monitoring system, you can achieve much more:

• Track smaller but frequent stops that add up to significant losses and often go undetected.
• Measure the production speed of your machines.
• See real-time OEE, visualized on the screen.
• Be sure that the data is complete and accurate, even when your staff do not have time to monitor production due to having more urgent tasks.

In short, automating production monitoring allows you to have more accurate production data, do more with it, and do it faster.

In other words, this is how you can achieve your full potential, which we talked about at the beginning of this article. Read more about how Evocon helps your company.

The Top 3 OEE Calculation Mistakes

We hope that our OEE calculator and explanations show how simple it is to calculate OEE. But we would like to point out that there is also room for mistakes.

As we mentioned above, manufacturers tend to overestimate their efficiency levels. The most common mistakes highlight some of the reasons for that:

1. Excluding stops from the Availability calculation. We often see that clients do not interpret stops such as product changeover, lunch, or rest breaks as Availability loss. Even though we can’t eliminate such stops from the processes completely, in the Six Big Losses framework they should still be treated as Availability losses. It is always possible to improve the process and reduce, for example, the changeover time and reorganize the work to avoid machines being stopped for coffee breaks (machines don’t drink coffee:).
2. Not using the real maximum speed (Nameplate Capacity, Ideal Cycle Time) when calculating the Performance. Quite often, we see that manufacturers use their internal target speed instead of the maximum. This results in incorrect Performance values above 100% when an automated OEE system is set up based on these values.
3. Leaving out the Quality component from the OEE calculation. This means that scrap and rework are not considered which can lead to unwanted results. There is always a link between quantity and quality. By focusing only on maximizing the output, we can say with confidence that the quality will start suffering and vice versa. That is why the OEE components also have a balancing effect in this context.

Besides these OEE calculation mistakes, you may find it useful to look into more typical mistakes of monitoring OEE.

How to Improve OEE?

Now that we have talked about measuring and calculating OEE, let’s take a look at how to improve it.

We have made a list of the 7 Best Practices to Improve OEE and Productivity from our clients:

1. Designating a champion for OEE implementation
2. Automating data collection and reporting
3. Visualizing and displaying real-time OEE on the shop floor
4. Commenting all production stops
5. Implementing cross-functional daily review and discussion sessions
6. Eliminating the Six Big Losses
7. Utilizing Root Cause Analysis

Your next steps to OEE improvement

Whether you used our calculator for a Simple OEE Calculation for a quick baseline or the Component Breakdown to find specific losses, knowing your numbers is only the first step.
Manual calculations are a great “snapshot,” but they can’t drive daily improvement. To truly get to your factory’s potential, you need to see these numbers live on the shop floor.

With an automated production monitoring system, you will be able to visualize the performance of your machines or production lines in real time and act based on accurate, reliable production data (as our clients did).

Now that you have a stronger understanding of OEE, check out our other resources on how to increase your OEE in practice:

• Evocon’s OEE Software ROI Calculator
• OEE Excel Template (Free Download)
• 3 Keys to Improving Production Quality in Manufacturing
• Downtime Tracking and Analysis – Find Out What’s Really Happening on the Shop Floor
• 3 Ways to Engage Production Operators and Improve OEE
• 3 Common Ways OEE Gets Manipulated — and How to Spot Them

Troubleshooting the OEE Calculator

You got a message saying “Should not exceed …”, and Performance is over 100%

The reason is that the sum of values in your “Quantity produced” and “Sum of scrap and rework” fields is too high.

If you are sure that your “Quantity produced” and “Sum of scrap and rework” are correct, try adjusting other settings:

• You could be underestimating your theoretical maximum speed. Try increasing it.
• Your working time may be set too low. Try increasing either “Working hours per day” or “Working days per month”.
• Or, you may have set your “Sum of all machine stops per day” too high. Try decreasing it.

You got a message “Speed set too low”, and Performance is over 100%

It is common among manufacturers to underestimate their theoretical maximum production speed which means that calculated Performance is more than 100%. But in the OEE framework, your Performance should never be above 100%.

How to find out your maximum production speed? 

Sometimes the manufacturer of the machine specifies it (alternative terms – “nameplate”, or “ideal cycle time”. If not, you can identify the fastest recorded time by looking at historical performance and then calculate how many products you would make if your machines were constantly running at that speed.

If you are sure that your maximum speed is correct, try adjusting other settings:

• Decreasing “Quantity produced per month” or “Sum of scrap or rework”
• Increasing “Working hours per day” or “Working days per month”
• Decreasing “Sum of all machine stops per day”

Back to the calculator

Frequently Asked Questions

1. What is a good OEE score?
   The world-class benchmark is 85%. That’s roughly 90% availability × 95% performance × 99% quality — which shows how little slack a top-tier production line leaves in any category. Our data shows that most manufacturers are closer to 55-60%.
   Whatever your score, the number itself matters less than the direction. Use your current OEE as the baseline, and measure every change against it. Constant improvement is the goal.
2. Can OEE be over 100%?
   No, your OEE score can never be over 100%. If your performance score is above 100%, this means that your speed targets are set incorrectly and need adjustment to get an accurate score. It is common among manufacturers to underestimate their theoretical maximum production speed, but in the OEE framework, your Performance should never be above 100%.
3. How do I calculate OEE in Excel?
   Though production monitoring systems are more efficient for tracking OEE, many manufacturers still use spreadsheets. To make this easier, we have created an OEE Excel Template, where you can simply enter a few key production figures — like working hours, good units produced, and theoretical maximum production speed, and the template automatically calculates your OEE components: availability, performance, quality, and overall OEE.
4. What’s the difference between OEE and TEEP?
   TEEP is a manufacturing metric that measures your equipment’s effectiveness against all available hours – 24 hours a day, 7 days a week. It considers every minute of every day, unlike OEE, which focuses on your planned production time. Learn more about the difference between TEEP, OOE, and OEE.