The 175 Principles of Flow

The book enumerates 175 principles in 8 categories. The easiest way to find each principle is to use the List of Principles on page 271. On page 271–276 the principles are listed in terse form. On this webpage all the principles are listed in their verbose form. Do let me know if this is useful, and if you would also like a downloadable PDF version. Thanks.


E1: The Principle of Quantified Overall Economics: Select actions based on quantified overall economic impact. (p.28)

E2: The Principle of Interconnected Variables: We can’t just change one thing. (p.29)

E3: The Principle of Quantified Cost of Delay: If you only quantify one thing, quantify the cost of delay. (p.31)

E4: The Principle of Economic Value-Added: The value added by an activity is the change in the economic value of the work product. (p.32)

E5: The Inactivity Principle: Watch the work product, not the worker. (p.33)

E6: The U-Curve Principle: Important trade-offs are likely to have U-curve optimizations. (p.35)

E7: The Imperfection Principle: Even imperfect answers improve decision making.(p.36)

E8: The Principle of Small Decisions: Influence the many small decisions.(p.36)

E9: The Principle of Continuous Economic Tradeoffs: Economic choices must be made continuously. (p.37)

E10: The First Perishability Principle: Many economic choices are more valuable when made quickly. (p.38)

E11: The Subdivision Principle: Inside every bad choice lies a good choice. (p.39)

E12: The Principle of Early Harvesting: Create systems to harvest the early cheap opportunities. (p.40)

E13: The Principle of Decision Rules: Use decision rules to decentralize economic control. (p.41)

E14: The First Market Principle: Ensure decision makers feel both cost and benefit. (p.42)

E15: The Principle of Optimum Decision Timing: Every decision has its optimum economic timing. (p.44)

E16: The Principle of Marginal Economics: Always compare marginal cost to marginal value. (p.45)

E17: The Sunk Cost Principle: Do not consider money already spent. (p.46)

E18: The Principle of Buying Information: The value of information is its expected economic value. (p.47)

E19: The Insurance Principle: Don’t pay more for  insurance than the expected loss. (p.49)

E20: The Newsboy Principle: High probability of failure does not equal bad economics. (p.50)

E21: The Show Me the Money Principle: To influence financial decisions, speak the language on money. (p.51)


Q1: The Principle of Invisible Inventory: Product development inventory is physically and financially invisible. (p.55)

Q2: The Principle of Queueing Waste: Queues are the root cause of the majority of economic waste in product development. (p.56)

Q3: The Principle of Queueing Capacity Utilization: Capacity utilization increases queues exponentially. (p.59)

Q4: The Principle of High-Queue States: Most of the damage done by a queue is caused by high-queue states. (p.61)

Q5: The Principle of Queueing Variability: Variability increases queues linearly. (p.62)

Q6: The Principle of Variability Amplification: Operating at high levels of capacity utilization increases variability. (p.64)

Q7: The Principle of Queueing Structure: Serve pooled demand with reliable high-capacity servers. (p.64)

Q8: The Principle of Linked Queues: Adjacent queues see arrival or service time variability depending on loading. (p.66)

Q9: The Principle of Queue Size Optimization: Optimum queue size is an economic tradeoff. (p.68)

Q10: The Principle of Queueing Discipline: Queue cost is affected by the sequence in which we handle the jobs in the queue. (p.69)

Q11: The Cumulative Flow Principle: Use CFDs to monitor queues. (p.71)

Q12: Little’s Formula: Wait time = Queue Size/Processing Rate. (p.73)

Q13: The First Queue Size Control Principle:  Don’t control capacity utilization, control queue size. (p.75)

Q14: The Second Queue Size Control Principle: Don’t control cycle time, control queue size. (p.76)

Q15: The Diffusion Principle: Over time, queues will randomly spin seriously out of control and will remain in this state for long periods. (p.76)

Q16: The Intervention Principle: We cannot rely on randomness to correct a random queue. (p.79)


V1: The Principle of Beneficial Variability: Variability can create economic value. (p.87)

V2: The Principle of Asymmetric Payoffs: Payoff asymmetries enable variability to create economic value. (p.88)

V3: The Principle of Optimum Variability: Variability should neither be minimized nor maximized. (p.91)

V4: The Principle of Optimum Failure Rate: Fifty percent failure rate is usually optimum for generating information. (p.92)

V5: The Principle of Variability Pooling: Overall variation decreases when uncorrelated random tasks are combined. (p.95)

V6: The Principle of Short-Term Forecasting: Forecasting becomes exponentially easier at short time-horizons. (p.96)

V7: The Principle of Small Experiments: Many small experiments produce less variation than one big one. (p.98)

V8: The Repetition Principle: Repetition reduces variation. (p.99)

V9: The Reuse Principle: Reuse reduces variability. (p.100)

V10: The Principle of Negative Covariance: We can reduce variance by applying a counterbalancing effect. (p.100)

V11: The Buffer Principle:Buffers trade money for variability reduction. (p.101)

V12: The Principle of Variability Consequence: Reducing consequences is usually the best way to reduce the cost of variability. (p.103)

V13: The Non-linearity Principle: Operate in the linear range of system performance. (p.104)

V14: The Principle of Variability Substitution: Substitute cheap variability for expensive variability. (p.105)

V15: The Principle of Iteration Speed: It is usually better to improve iteration speed than defect rate. (p.106)

V16: The Principle of Variability Displacement: Move variability to the process stage where its cost is lowest. (p.107)


B1: The Batch Size Queueing Principle: Reducing batch size reduces cycle time. (p.112)                                                                    124

B2: The Batch Size Variability Principle: Reducing batch size reduces variability in flow. (p.112)

B3: The Batch Size Feedback Principle: Reducing batch size accelerates feedback. (p.113)

B4: The Batch Size Risk Principle: Reducing batch size reduces risk. (p.114)

B5: The Batch Size Overhead Principle: Reducing batch size reduces overhead. (p.115)

B6: The Batch Size Efficiency Principle: Large batches reduce efficiency. (p. 115)

B7: The Psychology Principle of Batch Size: Large batches inherently lower motivation and urgency. (p.117)

B8: The Batch Size Slippage Principle: Large batches cause exponential cost and schedule growth. (p.,117)

B9: The Batch Size Death Spiral Principle: Large batches lead to even larger batches. (p.118)

B10: The Least Common Denominator Principle of Batch Size: The entire batch is limited by its worst element. (p.119)

B11: The Principle of Batch Size Economics: Economic batch size is a U-curve optimization. (p.121)

B12: The Principle of Low Transaction Cost: Reducing transaction cost per batch lowers overall costs. (p.123)

B13: The Principle of Batch Size Diseconomies: Batch size reduction saves much more than you think. (p.124)

B14: The Batch Size Packing Principle: Small batches allow finer tuning of capacity utilization (p.126)

B15: The Fluidity Principle: Loose coupling between product subsystems enables small batches. (p.126)

B16: The Principle of Transport Batches: The most important batch is the transport batch. (p.128)

B17: The Proximity Principle: Proximity enables small batch sizes. (p.129)

B18: The Run Length Principle: Short run lengths reduce queues. (p.130)

B19: The Infrastructure Principle: Good infrastructure enables small batches. (p.130)

B20: The Principle of Batch Content: Sequence first that which adds value most cheaply. (p.131)

B21: The Batch Size First Principle: Reduce batch size before you attack bottlenecks. (p.133)

B22: The Principle of Dynamic Batch Size: Adjust batch size dynamically to respond to changing economics. (p.135)


W1: The Principle of WIP Constraints: Constrain WIP to control cycle time and flow. (p.145)

W2: The Principle of Rate Matching: WIP constraints force rate-matching. (p.146)

W3: The Principle of Global Constraints: Use global WIP constraints for predictable and permanent bottlenecks. (p.147)

W4: The Principle of Local Constraints: If possible, constrain local WIP pools. (p.148)

W5: The Batch Size Decoupling Principle: Use WIP ranges to decouple the batch sizes of adjacent processes. (p.150)

W6: The Principle of Demand Blocking: Block all demand when WIP reaches its upper limit. (p.151)

W7: The Principle of WIP Purging: When WIP is high, purge low value projects. (p.151)

W8: The Principle of Flexible Requirements: Control WIP by shedding requirements. (p.152)

W9: The Principle of Resource Pulling: Quickly apply extra resources to an emerging queue. (p.153)

W10: The Principle of Part-Time Resources: Use part-time resources for high variability tasks. (p.153)

W11: The Big Gun Principle: Pull high-powered experts to emerging bottlenecks. (p.155)

W12: The Principle of T-Shaped Resources: Develop people who are deep in one area and broad in many. (p.155)

W13: The Principle of Skill Overlap: Cross train resources at adjacent processes. (p.156)

W14: The Mix Change Principle: Use upstream mix changes to regulate queue size. (p.156)

W15: The Aging Principle: Watch the outliers. (p.159)

W16: The Escalation Principle: Create a preplanned escalation process for outliers. (p.160)

W17: The Principle of Progressive Throttling: Increase throttling as you approach the queue limit. (p.161)

W18: The Principle of Differential Service: Differentiate quality of service by workstream. (p.161)

W19: The Principle of Adaptive WIP Constraints: Adjust WIP constraints as capacity changes. (p.162)

W20: The Expansion Control Principle: Prevent uncontrolled expansion of work. (p.163)

W21: The Principle of the Critical Queue: Constrain WIP in the secion of the system where the queue is most expensive. (p.164)

W22: The Cumulative Reduction Principle: Small WIP reductions accumulate. (p.165)

W23: The Principle of Visual WIP: Make WIP continuously visible. (p.166)


F1: The Principle of Congestion Collapse: When loading becomes too high, we will see a sudden and catastrophic drop in output. (p.172)

F2: The Peak Throughput Principle: Control occupancy to sustain high throughput in systems prone to congestion. (p.174)

F3: The Principle of Visible Congestion: Use forecasts of expected flow time to make congestion visible. (p.175)

F4: The Principle of Congestion Pricing: Use pricing to reduce demand during congested periods. (p.176)

F5: The Principle of Periodic Resynchronization: Use a regular cadence to limit the accumulation of variance. (p.177)

F6: The Cadence Capacity Margin Principle: Provide sufficient capacity margin to enable cadence. (p.178)

F7: The Cadence Reliability Principle: Use cadence to make waiting times predictable.(p.179)

F8: The Cadence Batch Size Enabling Principle: Use a regular cadence to enable small batch sizes. (p.179)

F9: The Principle of Cadenced Meetings: Schedule frequent meetings using a predictable cadence. (p. 180)

F10: The Synchronization Capacity Margin Principle: To enable synchronization, provide sufficient capacity margin. (p.187)

F11: The Principle of Multiproject Synchronization: Exploit scale economies by synchronizing work from multiple projects. (p.187)

F12: The Principle of Cross-Functional Synchronization: Use synchronized events to facilitate cross functional tradeoffs. (p.188)

F13: The Synchronization Queueing Principle: To reduce queues, synchronize the batch size and timing of adjacent processes. (p.189)

F14: The Harmonic Principle: Make nested cadences harmonic multiples. (p.190)

F15: The SJF Scheduling Principle: When delay costs are homogeneous, do the shortest job first. (p.192)

F16: The HDCF Scheduling Principle: When job durations are homogeneous, do the high cost-of-delay job first. (p.193)

F17: The WSJF Scheduling Principle: When job durations and delay costs are not homogeneous, use WSJF. (p.193)

F18: The Local Priority Principle: Priorities are inherently local. (p.196)

F19: The Round-Robin Principle: When task duration is unknown, time-share capacity. (p.196)

F20: The Preemption Principle: Only preempt when switching costs are low. (p.197)

F21: The Principle of Work Matching: Use sequence to match jobs to appropriate resources. (p.198)

F22: The Principle of Tailored Routing: Select and tailor the sequence of subprocesses to the task at hand. (p.199)

F23: The Principle of Flexible Routing: Route work based on the current most economic route. (p.200)

F24: The Principle of Alternate Routes: Develop and maintain alternate routes around points of congestion. (p.201)

F25: The Principle of Flexible Resources: Use flexible resources to absorb variation. (p.202)

F26: The Principle of Late Binding: The later we bind demand to resources, the smoother the flow. (p.202)

F27: The Principle of Local Transparency: Make tasks and resources reciprocally visible at adjacent processes. (p.204)

F28: The Principle of Preplanned Flexibility: For fast responses, preplan and invest in flexibility. (p.205)

F29: The Principle of Resource Centralization: Correctly managed, centralized resources can reduce queues. (p.206)

F30: The Principle of Flow Conditioning: Reduce variability before a bottleneck. (p.208)


FF1: The Principle of Maximum Economic Influence: Focus control on project and process parameters with the highest economic influence. (p.214)

FF2: The Principle of Efficient Control: Control parameters that are both influential and efficient. (p.215)

FF3: The Principle of Leading Indicators: Select control variables that predict future system behavior. (p.215)

FF4: The Principle of Balanced Set Points: Set tripwires at points of equal economic impact. (p.216)

FF5: The Moving Target Principle: Know when to pursue a dynamic goal. (p.218)

FF6: The Exploitation Principle: Exploit unplanned economic opportunities.(p.219)

FF7: The Queue Reduction Principle of Feedback: Fast feedback enables smaller queues. (p.220)

FF8: The Fast Learning Principle: Use fast feedback to make learning faster and more efficient. (p.221)

FF9: The Principle of Useless Measurement: What gets measured may not get done. (p.222)

FF10: The First Agility Principle: We don’t need long planning horizons when we have a short turning radius. (p.222)

FF11: The Batch Size Principle of Feedback: Small batches yield fast feedback. (p.223)

FF12: The Signal to Noise Principle: To detect a smaller signal, reduce the noise. (p.224)

FF13: The Decision Rule Principle: Control the economic logic behind the decision, not the entire decision. (p.225)

FF14: The Locality Principal of Feedback: Whenever possible make feedback local. (p.226)

FF15: The Relief Valve Principle: Have a clear, predetermined relief valve. (p.227)

FF16: The Principle of Multiple Control Loops: Embed fast control loops inside slow loops. (p.228)

FF17: The Principle of Controlled Excursions: Keep deviations within the control range. (p.229)

FF18: The Feedforward Principle: Provide advance notice of heavy arrival rates to minimize queues. (p.229)

FF19: The Principle of Colocation: Colocation improves almost all aspects of communications. (p.230)

FF20: The Empowerment Principle of Feedback: Fast feedback gives a sense of control. (p.231)

FF21: The Hurry-Up-and-Wait Principle: Large queues make it hard to create urgency. (p.232)

FF22: The Amplification Principle: The human element tends to amplify large excursions. (p.233)

FF23: The Principle of Overlapping Measurement: To align behaviors, reward people for the work of others. (p.233)

FF24: The Attention Principle: Time counts more than money. (p.234)


D1: The Second Perishability Principle: Decentralize control for problems and opportunities that age poorly. (p.246)

D2: The Scale Principle: Centralize control for problems that are infrequent, large, or that have significant economies of scale. (p.247)

D3: The Principle of Layered Control: Adapt the control approach to emerging information about the problem. (p.248)

D4: The Opportunistic Principle: Adjust the plan for unplanned obstacles and opportunities. (p.249)

D5: The Principle of Virtual Centralization: Be able to quickly reorganize decentralized resources to create centralized power. (p.250)

D6: The Inefficiency Principle: The inefficiency of decentralization can cost less than the value of faster response time. (p.251)

D7: The Principle of Alignment: There is more value created with overall alignment than local excellence. (p.252)

D8: The Principle of Mission: Specify the end state, its purpose, and the minimal possible constraints. (p.252)

D9: The Principle of Boundaries: Establish clear roles and boundaries. (p.253)

D10: The Main Effort Principle: Designate a main effort and subordinate other activities. (p.254)

D11: The Principle of Dynamic Alignment: The main effort may shift quickly when conditions change. (p.255)

D12 The Second Agility Principle: Develop the ability to quickly shift focus. (p.255)

D13: The Principle of Peer-Level Coordination: Tactical coordination should be local. (p.257)

D14: The Principle of Flexible Plans: Use simple modular plans. (p.258)

D15: The Principle of Tactical Reserves: Decentralize a portion of reserves. (p.258)

D16: The Principle of Early Contact: Make early and meaningful contact with the problem. (p.259)

D17: The Principle of Decentralized Information: For decentralized decisions, disseminate key information widely. (p.260)

D18: The Frequency Response Principle: We can’t respond faster than our frequency response. (p.261)

D19: The Quality of Service Principle: When response time is important, measure response time. (p.261)

D20: The Second Market Principle: Use internal and external markets to decentralize control. (p.262)

D21: The Principle of Regenerative Initiative: Cultivating initiative enables us to use initiative. (p.263)

D22: The Principle of Face-to-Face Communication: Exploit the speed and bandwidth of face-to-face communications. (p.263)

D23: The Trust Principle: Trust is built through experience. (p.264)

Copyright 2009, Donald G. Reinertsen