The problem: Forecast working capital using receivable, inventory and payable days linked to revenue and cost of sales — small day-count shifts can materially change cash projections.
Forecasting working capital by holding it flat or growing it with revenue ignores how businesses actually manage cash. A robust model links each working-capital line to an operational driver.
Why It Matters
Working capital is often the largest swing factor in projected free cash flow. Getting it wrong distorts valuation, liquidity planning and covenant testing.
Driver-Based Formulas
- Receivable days (DSO): Receivables = (Receivable days ÷ 365) × Revenue. Tighter collections reduce the cash tied up.
- Inventory days (DIO): Inventory = (Inventory days ÷ 365) × COGS. Faster turnover frees cash.
- Payable days (DPO): Payables = (Payable days ÷ 365) × COGS. Stretching payables preserves cash but strains supplier relationships.
- Net working capital: Receivables + Inventory − Payables. The period-over-period change flows into the cash flow statement.
Change in NWC = NWC(current) − NWC(prior) → flows into operating cash flowExample Assumptions
| Driver | Historical | Forecast |
|---|---|---|
| DSO (receivable days) | 52 days | 48 days |
| DIO (inventory days) | 38 days | 35 days |
| DPO (payable days) | 40 days | 42 days |
Key Takeaway
Forecast each working-capital line from its day-count driver and let the period-over-period change flow into cash — this keeps the model internally consistent and sensitive to real operational decisions.