Inventory Cash-Flow & Runway Calculator

First, the tool estimates weekly gross profit as: expected weekly sales velocity × gross margin percentage. Then it calculates net weekly cash flow as weekly gross profit − weekly operating cash burn. Finally, it compares starting cash to net weekly cash outflow to produce a runway (in weeks or months), and it also estimates an inventory sell-through timeframe using inventory on hand at cost.

Results assume steady sales week to week and a constant gross margin, so large promotions, seasonality, or markdowns can make the real runway shorter (or longer). It also assumes inventory converts to cash at the modeled pace without stockouts, returns, shrinkage, or lead-time shocks—real-world delays can reduce effective runway. Taxes, financing costs, payment terms (AR/AP), and supplier credit are not modeled unless you add them separately.

If expected weekly sales velocity is 0, the calculator avoids dividing by sales velocity and bases runway on cash burn alone. If inventory on hand is 0, it treats replenishment as immediate/none (you shouldn’t expect inventory to extend runway). If gross margin is 0%, all sales contribute no gross profit, so net cash flow becomes purely negative cash burn (or zero if burn is also zero).

Runway is sensitive to gross margin and burn rate: small changes in margin or operating costs can materially shift “safe vs at risk.” If your business relies on inventory lead times, staggered purchasing, or customer payment delays, your real cash runway may differ from the simplified model. Treat this as an early-warning planning tool and pair it with your purchasing schedule and payment timelines.