Working Capital and the Cash Conversion Cycle

A retailer buys inventory with cash today, sells it to customers on credit next month, and doesn't actually collect that cash until the month after. In between, the company is genuinely out of pocket — it has paid its supplier but hasn't yet been paid by its customer. That gap, measured in days, is the cash conversion cycle, and it's one of the most useful numbers for judging whether a growing company is going to need outside financing just to keep operating.

Working capital, defined

Working capital is current assets minus current liabilities — the short-term resources a company has available versus the short-term bills it owes. Net working capital in an operating sense usually excludes cash and short-term debt, focusing on the operating items: receivables and inventory on one side, payables on the other.

$$\text{Operating Working Capital} = (\text{Receivables} + \text{Inventory}) - \text{Payables}.$$

In words: money tied up in unpaid customer bills and unsold stock, net of the free financing suppliers provide by letting the company pay them later.

The cash conversion cycle

The cash conversion cycle (CCC) turns that balance-sheet snapshot into a timing measure, expressed in days:

$$\text{CCC} = \text{DIO} + \text{DSO} - \text{DPO}.$$

Days Inventory Outstanding (DIO) is how long inventory sits before it's sold. Days Sales Outstanding (DSO) is how long it takes customers to pay after a sale. Days Payable Outstanding (DPO) is how long the company takes to pay its own suppliers. Add the days cash is tied up (DIO, DSO) and subtract the days suppliers are effectively financing the company (DPO), and what's left is the number of days cash is stuck in the cycle before it comes back.

A worked example

A retailer holds average inventory of $40m against annual COGS of $300m: $\text{DIO} = 40/300 \times 365 \approx 49$ days. It holds average receivables of $25m against annual revenue of $400m: $\text{DSO} = 25/400 \times 365 \approx 23$ days. It holds average payables of $35m against the same $300m of COGS: $\text{DPO} = 35/300 \times 365 \approx 43$ days.

$$\text{CCC} = 49 + 23 - 43 = 29 \text{ days}.$$

Cash is tied up for about a month between paying for inventory and collecting from customers. If this retailer grows revenue by 20% next year, working capital needs grow roughly in proportion — inventory, receivables and payables all scale with sales — so the company needs new financing (from cash on hand, a credit line, or investors) just to fund that extra 29 days of cycle at the larger scale, even though the growth itself is profitable.

Why some businesses have negative cycles

Grocery chains and many subscription businesses often run a negative CCC: they collect from customers (immediately, at checkout, or via upfront subscription) before they have to pay suppliers. Amazon's retail business famously ran a deeply negative CCC for years — customers paid instantly while Amazon paid vendors on 60- or 90-day terms — which let the company fund enormous inventory growth almost entirely with supplier financing rather than its own capital.