Cash Flow Planning for Inventory-Based Businesses

Profit is an accounting concept. Cash is what pays your supplier. Inventory businesses fail on the gap between the two.

The Cash Conversion Cycle

Your cash is tied up from the moment you pay a supplier until the moment a customer's payment becomes available:

Cash Conversion Cycle = Inventory Days + Receivable Days − Payable Days

• Inventory days — how long stock sits before selling
• Receivable days — how long marketplace payouts take (Amazon: ~14 days)
• Payable days — how long you have to pay suppliers (often 0 for new sellers)

If you hold 60 days of inventory, wait 14 days for payout, and pay suppliers immediately, your cycle is 74 days. Every dollar you grow by is tied up for 74 days first.

Why Growth Consumes Cash

This is the counterintuitive part: growing faster makes cash worse.

If you sell $10,000/month with a 74-day cycle, you need roughly $24,600 in working capital just to sustain it. Double sales to $20,000/month and you need $49,200 — an extra $24,600 you must find, even though you are "profitable."

Calculating Your Inventory Investment

Cash in Inventory = Average Inventory Value × (Cycle Days ÷ 30)

Add the cost of inventory in transit, which is easy to forget — goods on a boat for 30 days are cash you cannot use.

Practical Planning Steps

1. Build a 13-Week Cash Forecast

Weekly, not monthly. Monthly forecasts hide the week you run out. List every expected inflow and outflow.

2. Stagger Purchase Orders

Do not reorder your whole catalog at once. Split orders so large outflows don't land in the same week as a payout gap.

3. Negotiate Payment Terms

Moving from upfront payment to net-30 with your supplier shortens your cycle by 30 days. That is often worth more than a 5% price discount.

4. Prioritize Fast-Moving SKUs

Every dollar in a slow mover is a dollar not working. Use the Inventory Turnover Calculator to rank SKUs by velocity and redirect capital to the fastest.

5. Keep a Cash Buffer

Target 1-2 months of fixed costs in reserve. Marketplace account holds and seasonal dips are routine, not exceptions.

The Metric to Watch Weekly

Track days of inventory on hand:

Days on Hand = Inventory Units ÷ Average Daily Units Sold

If it is rising while sales are flat, you are converting cash into unsold stock. That is the earliest signal of a cash crunch.

Tools

Use the Reorder Point Calculator to time purchases, and the Sell-Through Rate Calculator to catch velocity problems before they become cash problems.

Cash flow problems are almost always visible three months in advance. The mistake is not forecasting, not bad luck.