Twelve calculators built around the frameworks I use on every factory engagement — from Goldratt's Theory of Constraints to Deming's quality principles. All live-updating. No email required.
01Floor DiagnosticFirst numbers I calculate walking onto any production floor
OEE
Overall Equipment Effectiveness. The single most revealing number in a factory. World class = 85%+. Most plants run 45–65% without knowing it.
OEE72.7%
Availability
90%
Performance
85%
Quality
95%
OEE total
Benchmark: ≥85% world class · 60–85% typical · <60% needs attention
Nakajima, S. (1988). Introduction to TPM: Total Productive Maintenance. Productivity Press. · Jonsson, P. & Lesshammar, M. (1999). Evaluation and improvement of manufacturing performance measurement systems. International Journal of Operations & Production Management, 19(1).
Takt vs Cycle Time
Takt time is the drumbeat of customer demand. If your cycle time exceeds takt, you cannot meet demand — no matter how hard people work.
Takt time
13.5 min
Gap (takt − cycle)
+3.5 min
Gap %
+25.9%
Units / hour
6.0 /hr
Cycle time
Takt time
Goal: cycle time ≤ takt time. Buffer of 10–15% recommended.
Ohno, T. (1988). Toyota Production System: Beyond Large-Scale Production. Productivity Press. · Rother, M. & Shook, J. (1998). Learning to See: Value Stream Mapping. Lean Enterprise Institute.
Line Balance Efficiency
What % of labor time is value-adding vs. waiting. A 60% balanced line means 40% of your payroll is standing idle. Enter task times per station (up to 6).
Line Balance Efficiency78.4%
Balance loss
21.6%
Bottleneck CT
12.0 min
Total task time
47.5 min
St. 1
St. 2
St. 3
St. 4
St. 5
St. 6
Benchmark: ≥85% well-balanced. Gap = labor cost you're paying for nothing.
Boysen, N., Fliedner, M. & Scholl, A. (2007). A classification of assembly line balancing problems. European Journal of Operational Research, 183(2), 674–693. · Scholl, A. (1999). Balancing and Sequencing of Assembly Lines. Physica-Verlag.
02Where the Money's LeakingThe numbers that make ops managers sit forward in their chairs
Cost of Poor Quality
Most factories only track scrap. COPQ captures the full picture: internal failure, external failure, and appraisal. Typically 5–15% of revenue — and almost always a surprise.
Juran, J.M. & Gryna, F.M. (1988). Juran's Quality Control Handbook (4th ed.). McGraw-Hill. · ASQ (2019). Cost of Quality. American Society for Quality. · Feigenbaum, A.V. (1956). Total quality control. Harvard Business Review, 34(6), 93–101.
Rolled Throughput Yield
Multiply FPY across every process step. Six steps at 95% each = 73.5% RTY. Most managers don't know this number — and it's almost always worse than they expect.
Rolled Throughput Yield86.4%
Cumulative loss
13.6%
Steps counted
4 steps
After st.1
After st.2
After st.3
After st.4
After st.5
After st.6
Benchmark: ≥95% excellent. Every point below costs you real throughput.
Harry, M. & Schroeder, R. (2000). Six Sigma: The Breakthrough Management Strategy. Doubleday. · Breyfogle, F.W. (2003). Implementing Six Sigma (2nd ed.). Wiley. · Defect rates compound multiplicatively across process steps — a fundamental result of probability theory.
Bottleneck Downtime Cost
From Goldratt: an hour lost at the constraint is an hour lost for the entire system — forever. This converts every maintenance delay into a dollar figure.
Annual cost of constraint loss$677k
Cost per incident
$600
Downtime cost/mo
$4.8k
Starvation cost/mo
$30.7k
Goldratt: protect the constraint above all else. Every idle minute here is permanent lost throughput.
Goldratt, E.M. & Cox, J. (1984). The Goal: A Process of Ongoing Improvement. North River Press. · Goldratt, E.M. (1990). Theory of Constraints. North River Press. · Schragenheim, E. & Dettmer, H.W. (2001). Manufacturing at Warp Speed. CRC Press.
03Labor & CapacityAre you over-manned, under-manned, or running blind?
Manning Model
Given takt time and task times, how many operators do you actually need? Most lines are either over- or under-manned relative to demand.
Theoretical manning
3.7 operators
Excess operators
2.3 excess
Labor efficiency
61.7%
Theoretical
Actual
Goal: theoretical ≈ actual. Gap = labor spend with zero output.
Niebel, B.W. & Freivalds, A. (2003). Methods, Standards, and Work Design (11th ed.). McGraw-Hill. · Meyers, F.E. & Stewart, J.R. (2002). Motion and Time Study for Lean Manufacturing (3rd ed.). Prentice Hall.
Capacity Utilization
How much of your designed capacity are you actually using — and what is the hidden capacity worth? Above 85% utilization, lead time variability increases dramatically.
Capacity Utilization72.0%
Effective utilization
63.4%
Hidden capacity
28 units/hr
Hidden cap value/mo
$40.3k
Utilization
Effective util
Benchmark: 70–85% is the sweet spot. Above 85% = lead time risk. Below 70% = overcapacity.
Hopp, W.J. & Spearman, M.L. (2001). Factory Physics (2nd ed.). McGraw-Hill. Ch. 7 establishes the nonlinear relationship between utilization and cycle time (VUT equation). · Kingman, J.F.C. (1961). The single server queue in heavy traffic. Mathematical Proceedings of the Cambridge Philosophical Society, 57(4).
Direct Labor Efficiency
Standard hours earned vs. actual hours paid. A 70% DLE means your real labor cost is 43% higher than your standard cost assumes. Most costing models don't surface this.
Horngren, C.T., Datar, S.M. & Rajan, M.V. (2015). Cost Accounting: A Managerial Emphasis (15th ed.). Pearson. · Direct labor efficiency variance is a standard cost accounting concept codified in management accounting since the early 20th century.
04Inventory & MaterialCash tied up on the floor that most managers have stopped counting
Days on Hand
How many days of production you're carrying as inventory. 90+ days is almost always a problem — it means cash is sitting on shelves rather than working.
Womack, J.P. & Jones, D.T. (1996). Lean Thinking. Simon & Schuster. · Bragg, S.M. (2011). Financial Analysis: A Controller's Guide (2nd ed.). Wiley. · Industry benchmarks per APICS Supply Chain Management body of knowledge.
Inventory Carrying Cost
Most companies use 10% as their carrying cost rate. The real number — including capital, storage, obsolescence, and handling — is typically 20–30%. The difference is material.
Total carrying cost / yr$195.5k
Effective rate
23% of inventory
Capital cost
$68k
Storage cost
$51k
Obsolescence
$42.5k
Capital
Storage
Obsolescence
Handling
Reality check: true carrying cost is 20–30%/yr, not 10%. Underestimating distorts buy decisions.
Lambert, D.M. & Stock, J.R. (2001). Strategic Logistics Management (4th ed.). McGraw-Hill. · Ballou, R.H. (2004). Business Logistics/Supply Chain Management (5th ed.). Pearson. · Carrying cost components (capital, storage, obsolescence, handling) documented in Inventory Management literature since Harris (1913).
Safety Stock
The statistically correct buffer to hold given your demand variability and supplier lead time. Most safety stock decisions are made by gut feel — this is the math.
Silver, E.A., Pyke, D.F. & Peterson, R. (1998). Inventory Management and Production Planning and Scheduling (3rd ed.). Wiley. · Chopra, S. & Meindl, P. (2016). Supply Chain Management (6th ed.). Pearson. · Formula: SS = Z × σ_d × √LT, derived from normal distribution theory applied to stochastic demand.