The formulas, one factor at a time
OEE (Overall Equipment Effectiveness) measures how much of the planned time turns into good pieces at the ideal speed. The calculator breaks it into the three classic factors, each tied to one family of losses.
Run time = planned time − downtime
Availability = run time ÷ planned time
Performance = (ideal cycle time × pieces produced) ÷ run time
Quality = good pieces ÷ pieces produced
OEE = availability × performance × quality
- Availability: how much of the planned time the machine actually ran. Breakdowns, changeovers and material waits lower it.
- Performance: how fast it went, while running, against the ideal cycle. Slowdowns and micro-stops that often nobody records as downtime lower it.
- Quality: how many pieces came out good the first time. Scrap and rework lower it.
For the full explanation, with the losses behind each factor and the difference between OEE, OOE and TEEP, see the guide to calculating OEE.
Worked example: two presses, one total
The starting values describe two presses. The first runs a full shift: 450 planned minutes, 45 of downtime, an ideal cycle of 30 seconds, 729 pieces of which 700 good. The second runs half a shift: 240 planned minutes, 60 of downtime, an ideal cycle of 20 seconds, 500 pieces of which 480 good.
| Measure | Press 1 | Press 2 | Total |
|---|---|---|---|
| Planned time | 450 min | 240 min | 690 min |
| Run time | 405 min | 180 min | 585 min |
| Availability | 90.0% | 75.0% | 84.8% |
| Performance | 90.0% | 92.6% | 90.8% |
| Quality | 96.0% | 96.0% | 96.0% |
| OEE | 77.8% | 66.7% | 73.9% |
The simple average of the two OEE figures would give 72.2%, a value that matches no real time: it treats the second press's half shift as if it counted as much as the first press's full shift. Adding up minutes and pieces before dividing is the consistent way to combine different machines, shifts or days, and the Total row of the Excel template does the same.
What value to expect
The most quoted reference for discrete manufacturing is an OEE of 85%, called “world class” in the literature that goes back to Seiichi Nakajima's TPM: roughly 90% availability, 95% performance and 99.9% quality. It is neither a regulatory standard nor an average measured over a sample of companies: it is an order of magnitude, to be used with judgement.
Different processes have different values, and a manual assembly cell, a packaging line and a continuous plant rarely compare with each other. Usually the most useful comparison is the same machine against itself, week after week, with the same definitions of downtime and ideal cycle time.
The Excel template
The “Download the Excel template” button generates an .xlsx file with the rows you entered plus empty rows ready to fill. The file is created in your browser, without going through a server, and asks for no email address or sign-up.
- Columns A to F: the data to fill in, one row per machine, shift or day.
- Columns G to K: run time, availability, performance, quality and OEE, calculated with visible formulas you can change.
- Total row: adds up minutes and pieces before dividing, as the calculator does.
- Instructions sheet: the definition of each column and the formulas in plain words.
The formulas use only basic functions, sums and conditions, which spreadsheets that open the .xlsx format show in their own language.
From the spreadsheet to machine data
The calculator and the template help to understand the numbers and do the first sums. When OEE has to be followed every day, for every machine and every shift, copying part counts and stops by hand gets slow, and the data often arrives when the losses are already past.
With Muvia Industrial an edge node next to the line reads part counts and states from the PLCs, with the drivers for Siemens S7, OPC UA and Modbus TCP. Muvia has no packaged OEE module: your team writes the calculation once, in a Python function that a flow runs every morning per machine and shift, and the dashboard shows OEE and losses. The page OEE per shift from Siemens S7 PLCs walks through the path step by step, and a demo with an engineer can start from your machines.
Frequently asked questions
Add up the planned minutes, run minutes, pieces and ideal times of every machine, and divide only at the end, as the calculator's Total row does. That way each machine weighs as much as the time it was meant to produce. For a line of machines in series, OEE is usually measured on the bottleneck machine or at the line's output.
Because a simple average gives the same weight to a four-hour shift and an eight-hour one, or to a machine that runs little and one that runs all the time. In this page's example the average would give 72.2%, while the OEE of the whole time is 73.9%.
Enter one row per product or per order, each with its own ideal cycle time and its share of planned time and downtime, and read the total: the calculation adds up the ideal time of each row's pieces. It is the same logic as OEE written as the ideal time of the good pieces divided by the planned time.
No. The calculation and the Excel file are generated in your browser: the values are neither sent to Muvia nor stored. If you reload the page, the calculator starts again from the example.
Yes: it downloads without signing up or leaving an email address, and you can change and share it as you like.