Inventory Management A-Z: Supply Chain & Business Operations

Define inventory as stocks supporting production across the supply chain, including raw materials, work in progress, finished goods, service goods, and spare parts, and categorize by location, type, and function.

Explore how raw materials, work in progress, finished goods, and service supports inventory shape bakery operations, from ingredients like flour and eggs to consumables used in production.

Explore the types and forms of inventory across the supply chain, from raw materials and WIP to finished goods, including cycle, safety, pipeline, and anticipation inventory, and supplier locations.

Explore why inventory matters for availability, showcase products to customers, manage supplier minimum orders and lead times, and understand work-in-progress and Little's Law, with drop shipping as a no-inventory alternative.

Inventory protects against supply and demand uncertainty by buffering raw materials, work-in-progress, and finished goods, while exploiting price fluctuations and enabling level production and economies of scale.

Identify less good reasons for inventory, such as over-ordered raw materials and forecast errors. See how large work-in-progress, finished goods, and transport delays raise lead times and risk unsold stock.

Apply little's law to determine minimum work in progress from throughput rate and throughput time with L = Lambda W, and rearrange to W = L / Lambda for examples.

Use little's law on the camera factory: 1,000 per day, 2-day cycle, 3,000 wip; halving wip isn’t feasible with current throughput and time, so consider buffers protecting bottlenecks.

Evaluate how inventory incurs costs, including opportunity cost, cost of capital, obsolescence, handling, storage, insurance, and overheads. Businesses often estimate inventory cost at 20 to 30 percent of value annually.

Analyze the financial view of inventory as working capital, a current asset impacting liquidity and cash flow, and weigh the trade-off between inventory and available cash, considering opportunity cost.

Explore the operational costs of inventory by detailing ordering costs—from research to processing and delivery—alongside holding costs like storage, security, and depreciation.

Examine how whiskey aging in oak barrels increases value and profitability, with scotch rules, global inventories, and Scotland's 20 million barrels worth $50 billion, rising about 10% annually.

Learn how stock-outs across raw materials, WIP, finished goods, and service spares drive lost sales, delays, and blame, and apply balanced inventory aims to minimize holding costs.

Analyze how inventory costs, ordering, holding, and financing interact with stockout risks, as sales seeks instant availability, finance pursues liquidity, and production favors simplicity and steady stock batches.

Explore how the rock boat analogy reveals how excess inventory hides scheduling flaws and supplier unreliability, and why prudent, gradual reduction exposes problems to build leaner, lower-cost operations.

Explore metrics and KPIs for inventory management from a business perspective, covering inventory days, days on hand, inventory dollar days, shrinkage, and control charts.

Discover how metrics and KPIs provide numerical measures tracked over time to gauge overall business performance and inventory levels, track trends, and guide actions across finance, operations, and individuals.

Evaluate inventory performance from a business perspective by balancing availability and working capital, while tracking utilization, risk, and forecasting, scheduling, and purchasing for an actionable overview.

Explore popular inventory metrics including inventory turns, days on hand, inventory dollar days (IDD), throughput dollar days (TDD), GMROI, shrinkage, sell-through rate, product performance, and loss sales estimation.

Inventory turns measure sales relative to average inventory; higher turns signal better performance and can be calculated as sales over average inventory, with days on hand 365 divided by turns.

Analyze inventory turns by dividing COGS by average inventory value, convert to days on hand, and assess efficiency to guide inventory management decisions.

Monitor inventory levels over time with control charts, set upper and lower limits, and analyze deviations using the area above or below limits.

Explore inventory dollar days and throughput dollar days from the theory of constraints, and compute gross margin return on investment by dividing by average inventory value.

Inventory shrinkage occurs when the ending inventory differs from the physical count, caused by theft, errors, damage, or supplier fraud. Track shrinkage percentage, sell-through rate, and lost sales from stockouts.

Explore how different inventory types are classified by cost, importance, demand, and shelf life, including dependent vs independent demand, ABC classification, and runners, repeaters, and strangers.

Group inventory with abc analysis, dividing items into a, b, and c by value and sku count. Prioritize A parts, observe and adjust B parts, and replenish C parts.

Classify inventory into runners, repeaters, and strangers by demand frequency and production cadence. Runners require continuous replenishment with lean or JIT; repeaters follow regular, predictable schedules; strangers are ad hoc.

Differentiate independent demand from dependent demand by showing how the independent demand for a car drives sub-assemblies and raw materials, which are dependent on that demand.

Learn how the bill of materials links independent demand items to dependent components, enabling materials requirements planning and master production scheduling for purchasing, work orders, and reporting.

Explore inventory dynamics by examining demand rate, re-order points, safety stock, and lead times, and learn how these factors interact to predict inventory levels over time.

Analyze inventory dynamics as stock follows a sawtooth pattern; demand rate governs depletion to the reorder point (ROP), time between orders, replenishment lead time, and average inventory Q/2.

Explore how order size and frequency impact inventory levels, demand rate, and replenishment timing, and learn about safety stock and reorder points to prevent stockouts.

Explore how much to order by applying the economic order quantity model, the first key decision in inventory purchasing within supply chain and operations.

Apply the economic order quantity model to minimize total inventory costs by balancing holding costs and ordering costs, using the EOQ formula sqrt(2DS/H).

Calculate the EOQ using an ice cream example, balancing ordering costs and holding costs to minimize monthly total cost.

The economic order quantity (EOQ) computes near-optimal order size using demand, setup and holding costs, showing insensitivity to small input changes and deriving time between orders from Q/D.

Explore how batch sizes drive work in progress, lead time, and quality risk across manufacturing and services. Compare single item versus mega batches and learn how changeovers and throughput matter.

Explore the economic batch quantity model and its setup and holding costs. Analyze its demand-based formula, limitations on lead time and customer delivery, and note alternatives in lean manufacturing.

Examine order quantity decisions beyond EOQ, including the price break model, container size constraints, cash availability, and fixed-interval ordering.

Explore how the price break model extends the economic order quantity by incorporating quantity discounts, ordering costs, holding costs, purchasing costs, and price bands to minimize total cost.

Compare price break options against the EOQ to minimize total cost, revealing that ordering 5,000 units at $0.90 yields the lowest total cost.

Explore the PBM curve, showing how total cost combines ordering and holding costs across price tiers, with the minimum at 5,000 units and 10,500 total cost.

Apply the price break model to determine the optimal order size by comparing EOQ with quantity discounts, balancing ordering, holding, and purchasing costs to minimize total cost.