Cash Flow Forecast Calculator
Model monthly cash inflows vs. outflows for your ecommerce business.
Results
Visualization
How It Works
Cash flow is the actual movement of money into and out of your business each month. Positive cash flow means more money came in than went out — the business is self-sustaining. Negative cash flow (burn) means you're spending down your reserves. Even profitable ecommerce stores can have negative cash flow in months with large inventory purchases, which is why forecasting matters.
The Formula
Variables
- Rev — Monthly Revenue — all cash collected from customers
- COGS% — Cost of Goods Sold % — percentage of revenue paid to suppliers for the items sold
- OpEx — Fixed Operating Expenses — rent, software, salaries, subscriptions
- Ads — Monthly Ad Spend — paid marketing budget
- Inv — Inventory Purchases — cash paid for inventory this month (not necessarily what was sold)
- PF% — Payment Processing Fee % — Stripe/PayPal typically charge ~2.9% + $0.30 per transaction
Worked Example
A store earns $20,000/month. COGS is 40% ($8,000), operating expenses $3,000, ad spend $2,000, inventory purchase $5,000, processing fees 2.9% ($580). Total outflows = $18,580. Net cash flow = $20,000 - $18,580 = $1,420 positive. With $15,000 in the bank, runway is well over 12 months even in a down month.
Practical Tips
- Separate inventory purchases from COGS — inventory is cash out now, but COGS is only recognized when the item sells. Heavy pre-season stocking creates temporary negative cash flow even when sales are strong.
- Negotiate net-30 or net-60 payment terms with suppliers to smooth cash flow — you collect from customers before you pay suppliers.
- Build a 3-month cash reserve (3× your monthly burn rate) to buffer against slow months, ad account suspensions, or supply chain delays.
- Ad spend is often your most adjustable outflow — in a cash crunch, you can cut ad spend immediately without operational disruption.
- Track cash flow weekly, not just monthly — a single large inventory payment can temporarily drain your account even in a profitable month.
Frequently Asked Questions
What's the difference between profit and cash flow?
Profit is revenue minus expenses on an accrual basis — it counts sales when made and costs when incurred, regardless of when cash moves. Cash flow tracks actual money in and out. An ecommerce store can be profitable but cash-flow negative if it just bought $30,000 in inventory that hasn't sold yet. Both metrics matter for different decisions.
What is a burn rate?
Burn rate is the monthly rate at which you're spending down cash reserves when outflows exceed inflows. If your net cash flow is -$3,000/month and you have $18,000 in the bank, your runway is 6 months. Knowing your burn rate is critical for timing fundraising, credit line draws, or cost-cutting decisions.
Why does my ecommerce store have negative cash flow even though it's profitable?
The most common reason is inventory timing. If you buy $15,000 of holiday inventory in October, your October cash flow is negative even though the inventory will generate profit in November and December. This is a working capital issue, not a profitability issue — it's solvable with credit lines, supplier terms negotiation, or staged inventory purchases.
How do I improve ecommerce cash flow?
Key levers: (1) negotiate longer payment terms with suppliers, (2) collect from customers faster (instant payment via checkout vs. invoice), (3) reduce inventory levels through better demand forecasting, (4) use a business credit card with a 30-day float for ad spend, and (5) reduce processing fees by negotiating with your payment processor at scale.
What should I include in operating expenses?
Include all fixed monthly costs: Shopify/WooCommerce subscription, app fees (reviews, email, analytics tools), warehouse rent or 3PL monthly minimum, salaries and contractor fees, accounting software, domain and hosting, customer service platform, and insurance. Don't include COGS, ad spend, or inventory — those are separate line items with different cash flow timing.