BIZOMAT Tools · Operations
OEE and Downtime Analysis
How effectively is this production asset being used?
Calculates OEE from raw production data and shows where the planned time went, with data checks and downtime cost.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Planned production time | min | Planned production time (excluding planned breaks) |
| Downtime | min | Unplanned and changeover stoppages from the downtime log |
| Ideal cycle time | sec/unit | Design or best demonstrated cycle time in seconds |
| Total units produced | units | Units produced (counter) |
| Good units | units | Units right first time (quality records) |
| Estimated downtime cost | $/hr | Cost of one hour of downtime (lost contribution plus idle cost) |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Planned production time
- What it is
- The time the equipment was scheduled to run in the period, after planned breaks and planned no-production time are removed.
- Units and format
- Enter a number in min: minutes. The form accepts 1 min or more.
- Example
- The form opens with 480 min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Availability is run time ÷ planned time, so this is the base for all three factors.
- Get it right
- Exclude planned breaks; include changeovers, because they are counted as downtime.
What this means: Downtime
- What it is
- Minutes the equipment was stopped during planned time: breakdowns, changeovers, waiting for material and other stops, from the downtime log.
- Units and format
- Enter a number in min: minutes. The form accepts 0 min or more.
- Example
- The form opens with 60 min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Each minute lowers availability and adds to downtime cost.
- Get it right
- It cannot exceed planned time; the tool flags the data if it does.
What this means: Ideal cycle time
- What it is
- The fastest time the equipment can make one unit, from the design rating or the best sustained rate demonstrated.
- Units and format
- Enter a number in sec/unit: sec/unit. The form accepts 0.01 sec/unit or more.
- Example
- The form opens with 30 sec/unit as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Performance rises in proportion to the ideal cycle time.
- Get it right
- Enter seconds, not minutes. Too long an ideal cycle pushes performance over 100 % and flags the data.
What this means: Total units produced
- What it is
- Every unit the equipment produced in the planned time, good or bad, from the machine counter.
- Units and format
- Enter a number in units: a count of units. The form accepts 0 units or more.
- Example
- The form opens with 700 units as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More units raise performance but lower quality if good units stay the same.
- Get it right
- Include scrap and rework units; the good count is entered separately.
What this means: Good units
- What it is
- Units that passed first time without rework or scrap, from quality records.
- Units and format
- Enter a number in units: a count of units. The form accepts 0 units or more.
- Example
- The form opens with 665 units as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Quality is good ÷ total, so it rises in proportion.
- Get it right
- It cannot exceed the total count. Reworked units are not good units here.
What this means: Estimated downtime cost
- What it is
- The money lost for each hour the equipment is down: lost contribution on missed output plus idle labour and other running costs.
- Units and format
- Enter a number in $/hr: money per hour. The form accepts $0/hr or more.
- Example
- The form opens with $180/hr as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Downtime cost is downtime hours × this rate; it does not change OEE.
- Get it right
- Agree the rate with finance; using full selling price overstates the loss if the output can be recovered later.
Method and formulas
- Availability = (planned − downtime) ÷ planned
- Performance = ideal cycle × total ÷ run time (capped at 100%)
- Quality = good ÷ total
- OEE = availability × performance × quality = fully productive time ÷ planned time
Limitations
- Performance above 100% indicates an ideal cycle time that is too long or a wrong count
- Rework counts as a quality loss
Typical uses
- Weekly OEE reporting
- Finding the biggest loss on a machine
- Valuing downtime
Who it is for
- Maintenance and production managers
- Continuous-improvement teams
What you get
- OEE and its three factors
- Time-loss table
- Data checks and downtime cost
Interpreting the result
- Attack the largest loss in the time table first
- Fix data faults before acting on the numbers
References
- Nakajima S., Introduction to TPM: Total Productive Maintenance (Productivity Press, 1988)
Learn the Concepts Behind This Tool
These BIZOMAT Library readings explain the method this tool uses, with worked examples.
Method explained here · Library collection
Measuring productivity: output per input, labour measures and overall equipment effectiveness
In Lean, Maintenance and Continuous Improvement
What it covers: How to measure productivity in a small business or factory: the output–input formula, choosing the right measures, OEE with a worked example, the six big losses, and avoiding perverse targets.
Method explained here · BIZOMAT original book
Proving the pilot: acceptance tests and run length
In Modular Projects by the Numbers
What it covers: Plan FAT, SAT and SIT for a packing cell, test 10 cases a minute and a pallet every 6 minutes, and size the run by the rule of three: 24 hours to show 1 stoppage in 8.
Method explained here · BIZOMAT original book
Working back from the gap to its causes
In Outcome-First Projects by the Numbers
What it covers: A Pareto of 412 failed deliveries and a capacity check on effective rates: ironers and dispatch cause 83%, the ironers are 20% short on peak days, and the washers are not the constraint.
Method explained here · Library collection
Putting a dollar value on equipment losses: using OEE to guide capacity and capital decisions
In Valuing Time, Delay and Uncertainty
What it covers: An OEE percentage shows capacity is being lost, not what the loss is worth. How to value downtime, speed and quality losses, focus on the constraint and check before buying equipment.
Useful alongside · BIZOMAT original book
More states and the balance equations
In Breakdowns and Buffers by the Numbers
What it covers: Splitting stops into minor jams and breakdowns: a three-state Markov model, its balance equations and detailed balance, slower settling, long-stop risk, and availability inside OEE.
Learning pathway
Measure and value equipment losses
Learn how OEE separates availability, performance and quality losses, then analyse a production period of your own.
1 Learn
Read Measuring productivity: output per input, labour measures and overall equipment effectiveness in Lean, Maintenance and Continuous Improvement.
How to measure productivity in a small business or factory: the output–input formula, choosing the right measures, OEE with a worked example, the six big losses, and avoiding perverse targets.
2 Apply
Open OEE and Downtime Analysis and enter your own figures.
How effectively is this production asset being used?
3 Verify
Read the tool’s feasibility and verification checks under the result, and test your answer against its stated limitations:
- Performance above 100% indicates an ideal cycle time that is too long or a wrong count
- Rework counts as a quality loss
4 Improve
Download the decision report or copy the link with your inputs to keep a record, then change one assumption at a time and compare.
Next reading: Putting a dollar value on equipment losses: using OEE to guide capacity and capital decisions in Valuing Time, Delay and Uncertainty.
BIZOMAT tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.