Net working capital (NWC) is one of the most misunderstood line items in finance interviews — candidates can define it correctly ("current assets minus current liabilities") but still get tripped up when asked whether a change in NWC is a source or a use of cash. Understanding the mechanics behind NWC, and the related concept of the Cash Conversion Cycle (CCC), is essential for accounting, FP&A, and even DCF-modeling interviews.

What Net Working Capital Actually Measures

At its core, NWC captures how much cash is tied up in the day-to-day operating cycle of a business — the gap between when a company pays cash out (for inventory, supplies, wages) and when it collects cash in (from customers). The most common operating definition used in interviews is:

NWC = Accounts Receivable + Inventory − Accounts Payable

Each component ties to one of the three financial statements: Accounts Receivable and Inventory sit on the asset side of the Balance Sheet, while Accounts Payable sits on the liability side. When NWC increases, a company has tied up more cash in operations than it has collected — a use of cash. When NWC decreases, cash is freed up — a source of cash.

The Cash Conversion Cycle: Turning NWC Into Days

While NWC gives you a dollar figure, the Cash Conversion Cycle expresses the same idea in days, which makes it far easier to compare across companies of different sizes. It's built from three components:

  • Days Sales Outstanding (DSO) — how long it takes to collect cash from customers after a sale
  • Days Inventory Outstanding (DIO) — how long inventory sits before being sold
  • Days Payable Outstanding (DPO) — how long the company takes to pay its own suppliers

Put together: CCC = DSO + DIO − DPO. A shorter CCC generally means a company is more efficient at converting operating activity into cash — it's collecting from customers faster and/or paying suppliers slower than it's holding inventory.

Why This Matters Beyond the Balance Sheet

Interviewers rarely ask about NWC in isolation — it usually comes up in the context of building an unlevered Free Cash Flow forecast, where the change in NWC is subtracted (or added back, if NWC decreased) alongside D&A and CapEx adjustments. If you haven't already, it's worth reviewing how Net Income bridges to Free Cash Flow from the Statements, since NWC changes are one of the three core adjustments in that build, alongside the Cash Flow Statement mechanics more broadly.

To see the full mechanics worked through with real numbers — computing DSO, DIO, DPO, and the resulting change in NWC across two years — walk through the Working Capital Deep Dive case, which uses a two-year balance sheet comparison to show exactly how a lengthening Cash Conversion Cycle shows up as a use of cash.