Working capital trapped in inventory: from raw materials to cash

The formula:

CCC = DIO + DSO − DPO

A shorter CCC means cash returns faster. A longer CCC means more working capitalworking capitalWorking capital is the difference between a company's current assets and current liabilities, measuring short-term liquidity and the funds available to run daily operations.View full definition → (the money funding day-to-day operations) is trapped, often financed by a revolving credit line that charges interest.

For a discrete manufacturer (one that makes countable, distinct units like pumps, motors, or appliances, as opposed to continuous process output like chemicals), DIO is usually the villain. Inventory does not sit as one lump. It sits in three separate buffers.

The three buffers where cash hides

1. Raw materials

Steel, castings, fasteners, electronic components. A factory holds safety stock (extra inventory kept as a cushion against demand spikes or late deliveries) to avoid shutting a line down when a supplier slips.

Concrete example: a discrete manufacturer buys aluminum extrusions with a 6-week lead time from a single overseas supplier. To protect against a missed shipment, it holds 8 weeks of stock. That is roughly 56 days of raw-material cash sitting on shelves before a single part is even cut.

The finance question is simple: what does that cushion cost? If those extrusions represent $2 million of the balance sheet and the company borrows at, say, an estimated 8 percent on its credit line, the carrying cost of financing alone is about $160,000 a year, before you count warehouse space, insurance, and obsolescence.

2. Work in process (WIP)

WIP is inventory that has entered production but is not finished. This is where long production runs quietly trap cash.

Why do factories run long batches? To spread setup cost (the time and labor to change a machine over from one product to another) across more units. If a stamping press takes 4 hours to retool, running 10,000 parts instead of 1,000 lowers cost per part.

But long runs create a hidden bill. Make 10,000 brackets when the customer needs 1,000 this month, and 9,000 brackets sit as WIP or finished goods for weeks. The "efficiency" of the long run converted directly into trapped working capitalworking capitalWorking capital is the difference between a company's current assets and current liabilities, measuring short-term liquidity and the funds available to run daily operations.View full definition →.

This is the classic tension between unit cost (looks great with long runs) and cash velocity (looks terrible with long runs). Traditional cost accounting rewards the first and ignores the second. That is exactly why finance and operations often argue past each other.

3. Finished goods

Completed products waiting to ship. Some finished-goods stock is deliberate: you promise 2-day delivery, so you stock ahead. Some is accidental: you built to a forecast that did not materialize.

The dangerous kind is obsolescence risk. A finished appliance model that gets replaced by a new version can become deadstock, written down to scrap value. That is not just trapped cash, it is destroyed cash.

Putting numbers on the trap

Let us build a simple, illustrative CCC for a discrete manufacturer. These figures are made up to show the method, not to represent any real firm.

| Stage | Days of inventory |

|---|---|

| Raw materials | 56 |

| WIP | 20 |

| Finished goods | 34 |

| Total DIO | 110 |

Add DSO of 45 days (customers pay in 45) and subtract DPO of 40 days (you pay suppliers in 40):

CCC = 110 + 45 − 40 = 115 days

So this factory waits 115 days between paying for material and collecting cash. If it does $50 million in annual cost of goods sold, roughly $137,000 in cost flows out per day. A 115-day cycle means about $15.8 million of working capitalworking capitalWorking capital is the difference between a company's current assets and current liabilities, measuring short-term liquidity and the funds available to run daily operations.View full definition → is tied up at any moment. Shave 15 days off the cycle and you free roughly $2 million in cash, permanently, without selling a single extra unit.

That is the pitch every operations improvement should make to a CFO: not "we saved labor," but "we released cash."

Where lean releases the cash

Lean manufacturing is a set of practices aimed at reducing waste, including the waste of excess inventory. Financially, lean is a working-capital release engine. Here is where it acts on each buffer.

Shrinking raw-material safety stock

Lean pushes toward just-in-time (JIT) delivery, where suppliers deliver smaller quantities more often, closer to when material is actually consumed. Dropping raw-material coverage from 56 days to 30 days directly cuts DIO by 26 days.

The catch: JIT trades inventory risk for supply-chain risk. The 2020 to 2022 disruptions taught manufacturers that razor-thin buffers snap under stress. The modern answer is segmented safety stock: thin buffers on reliable, local, low-value items; deeper buffers on single-sourced, long-lead, critical parts. You spend your cushion where it protects the most revenue.

Shortening production runs with faster changeovers

The tool here is SMED (Single-Minute Exchange of Die), a method for cutting machine setup time dramatically, sometimes from hours to minutes. When a changeover drops from 4 hours to 20 minutes, small batches stop being expensive. You can make 1,000 brackets economically instead of 10,000, and WIP plus finished-goods inventory collapses.

Toyota's original playbook popularized these ideas. The Lean Enterprise Institute offers free introductory material on the core concepts if you want the operations grounding.

Pulling instead of pushing

A pull system (often signaled by kanban, a visual card or bin trigger) replenishes only what downstream demand has actually consumed. Push systems build to forecast and pile up finished goods. Pull systems build to real orders and keep finished-goods stock lean, cutting obsolescence risk at the same time.

The finance-operations bridge

Here is the strategic point most factories miss. Lean is usually sold internally as an operations or quality program. Framed that way, it competes for attention with a dozen other initiatives.

Reframe it as balance-sheet strategy and it wins funding fast. Every day removed from the cash conversion cycle is cash that no longer needs to be borrowed. In a higher-interest-rate environment like the one manufacturers have navigated into 2026, that released cash carries a real, measurable financing cost saving.

A useful discipline: attach a cash tag to every operations project. Instead of "reduce WIP by 30 percent," write "reduce WIP by 30 percent, releasing an estimated $1.4 million and cutting annual interest cost by an estimated $110,000." Now the plant manager and the CFO are reading the same sentence.

Two cautions:

• Do not confuse inventory reduction with demand collapse. If sales fall, inventory also falls, but that is bad news, not a lean win. Always read DIO alongside actual throughput.
• A very short CCC can hide fragility. Stretching supplier payments (raising DPO) shortens the cycle on paper but can strain the suppliers you depend on. Cheap cash today, brittle supply chain tomorrow.

Key takeaways

• Inventory is frozen cash. In a discrete manufacturer, DIO (raw materials plus WIP plus finished goods) is usually the biggest driver of a long cash conversion cycle.
• Safety stock and long production runs are the two main traps. Both look rational in isolation (protect the line, lower unit cost) while quietly locking up working capitalworking capitalWorking capital is the difference between a company's current assets and current liabilities, measuring short-term liquidity and the funds available to run daily operations.View full definition →.
• Days translate directly into dollars. Multiply days removed from the CCC by daily cost of goods sold to size the cash release, then apply your borrowing rate to size the interest saving.
• Lean is a working-capital tool, not just an operations tool. JIT, SMED, and pull systems each attack a specific buffer. Segment your safety stock so you cut cash without cutting resilience.
• Tag every improvement with its cash impact. That is the language that aligns the factory floor and the finance office.