Calculating Oee

OEE Calculator

Overall Equipment Effectiveness (OEE) is a measure of how effectively a manufacturing operation is utilized. It identifies the percentage of manufacturing time that is truly productive. An OEE score of 100% means you are manufacturing only Good Parts, as fast as possible, without Stop Time.

OEE is calculated as the product of three factors: Availability, Performance, and Quality.

Planned Production Time (minutes):

Total time the equipment was scheduled to run, excluding planned breaks.

Downtime (minutes):

Time the equipment was stopped due to breakdowns, changeovers, or other unplanned stops.

Total Units Produced:

Total number of items produced (including both good and defective units).

Defective Units:

Number of items produced that are defective and require rework or scrap.

Ideal Cycle Time (seconds/unit):

The theoretical fastest time to produce one unit under optimal conditions.

OEE Results:

Availability: —

Performance: —

Quality: —

Overall Equipment Effectiveness (OEE): —

Understanding Overall Equipment Effectiveness (OEE)

Overall Equipment Effectiveness (OEE) is a powerful metric that provides deep insights into how well your manufacturing operations are performing. It's a cornerstone of Lean Manufacturing and TPM (Total Productive Maintenance) methodologies, helping businesses identify and eliminate waste, improve productivity, and enhance profitability.

The Three Pillars of OEE

OEE is comprised of three critical components, each representing a different aspect of productivity loss:

Availability: This factor accounts for downtime losses, which are any events that stop planned production for a measurable period of time. Examples include equipment breakdowns, material shortages, changeovers, and setup times. Availability is calculated as:
Availability = Operating Time / Planned Production Time
Where Operating Time = Planned Production Time – Downtime.
Performance: This factor accounts for speed losses, which occur when equipment runs slower than its ideal cycle time. This includes minor stops (brief pauses in production) and reduced speed (running below the theoretical maximum speed). Performance is calculated as:
Performance = (Total Units Produced / Target Production)
Where Target Production = Operating Time × Ideal Production Rate (based on Ideal Cycle Time).
Quality: This factor accounts for quality losses, which are defects or rework. It measures the percentage of good units produced compared to the total units started. Quality is calculated as:
Quality = Good Units / Total Units Produced
Where Good Units = Total Units Produced – Defective Units.

Once you have calculated Availability, Performance, and Quality, OEE is simply their product:

OEE = Availability × Performance × Quality

The result is typically expressed as a percentage. A higher OEE score indicates more efficient and productive manufacturing.

Why is OEE Important?

Identifies Hidden Losses: OEE helps uncover the "six big losses" in manufacturing: breakdowns, setup and adjustment, minor stops, reduced speed, process defects, and reduced yield.
Benchmarking: It provides a standardized way to compare the performance of different machines, lines, or even plants over time.
Continuous Improvement: By pinpointing areas of inefficiency, OEE guides improvement efforts, allowing teams to focus on the most impactful changes.
Increased Profitability: Optimizing OEE directly leads to higher output, lower costs, and better utilization of assets.

Example Calculation:

Let's use the default values in the calculator:

Planned Production Time: 480 minutes
Downtime: 60 minutes
Total Units Produced: 1000 units
Defective Units: 50 units
Ideal Cycle Time: 20 seconds/unit

1. Calculate Availability:

Operating Time = Planned Production Time – Downtime = 480 – 60 = 420 minutes
Availability = Operating Time / Planned Production Time = 420 / 480 = 0.875 or 87.5%

2. Calculate Performance:

Ideal Cycle Time (minutes/unit) = 20 seconds / 60 seconds/minute ≈ 0.3333 minutes/unit
Ideal Production Rate = 1 / Ideal Cycle Time (minutes/unit) = 1 / 0.3333 ≈ 3 units/minute
Target Production = Operating Time × Ideal Production Rate = 420 minutes × 3 units/minute = 1260 units
Performance = Total Units Produced / Target Production = 1000 / 1260 ≈ 0.7937 or 79.37%

3. Calculate Quality:

Good Units = Total Units Produced – Defective Units = 1000 – 50 = 950 units
Quality = Good Units / Total Units Produced = 950 / 1000 = 0.95 or 95%

4. Calculate OEE:

OEE = Availability × Performance × Quality = 0.875 × 0.7937 × 0.95 ≈ 0.6599 or 65.99%

This example demonstrates how each factor contributes to the overall OEE score, highlighting areas for potential improvement.

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Calculate Availability var operatingTime = plannedProductionTime – downtime; var availability = 0; if (plannedProductionTime > 0) { availability = operatingTime / plannedProductionTime; } else { availability = 0; // If no planned time, availability is 0 } // 2. Calculate Performance var idealCycleTimeMinutes = idealCycleTime / 60; // Convert seconds/unit to minutes/unit var idealProductionRate = 1 / idealCycleTimeMinutes; // units per minute var targetProduction = operatingTime * idealProductionRate; // Total units that *should* have been produced var performance = 0; if (targetProduction > 0) { performance = totalUnitsProduced / targetProduction; } else if (totalUnitsProduced > 0 && operatingTime === 0) { // This scenario implies units were produced with no operating time, which is inconsistent. // However, if operatingTime is 0, availability is 0, making OEE 0 regardless. // For performance itself, if target is 0 but actual is >0, it's often capped at 1. performance = 1; } else { performance = 0; // If target production is 0 and total units is 0, or target is 0 and operating time is 0 } // Cap performance at 1 (100%) as it cannot exceed ideal rate if (performance > 1) { performance = 1; } // 3. Calculate Quality var goodUnits = totalUnitsProduced – defectiveUnits; var quality = 0; if (totalUnitsProduced > 0) { quality = goodUnits / totalUnitsProduced; } else { quality = 0; // If no units produced, quality is 0 } // 4. Calculate OEE var oee = availability * performance * quality; // Display results document.getElementById('availabilityResult').innerText = (availability * 100).toFixed(2) + '%'; document.getElementById('performanceResult').innerText = (performance * 100).toFixed(2) + '%'; document.getElementById('qualityResult').innerText = (quality * 100).toFixed(2) + '%'; document.getElementById('oeeFinalResult').innerText = (oee * 100).toFixed(2) + '%'; } // Run calculation on page load with default values window.onload = calculateOEE;