Cash Flow Calculator — 12-Month Projection with Visual Chart

How it works

Enter your opening cash balance, then estimated income and expenses for each of the next 12 months. The calculator keeps a running balance and highlights the month where your cash is lowest. The chart below shows the running balance over the year — anything below the red dashed line is a cash crisis warning.

Common mistakes

• Booking income in the invoice month — an invoice raised on 30 January with net-30 terms is cash in late February or early March, not January. Owners habitually enter revenue when sold rather than when paid, which makes the projection look 30–60 days better than reality. Always model income in the month cash actually arrives, with a 15–20% late-payment buffer.
• Modelling tax payments only annually — UK VAT is quarterly, US federal estimated taxes are quarterly, SA VAT is bi-monthly or monthly. Each of these creates a large lumpy outflow that wrecks the month it lands in if planned as a year-end item. Add the actual due-date months explicitly.
• Treating credit-line drawdowns as income — drawing $20,000 from an overdraft or line of credit is borrowing, not revenue. It increases cash today and must be repaid (with interest) later. Track financing inflows and outflows on a separate line so the operating cash flow signal stays clean.

When to use this calculator

Use this when you need a 12-month view of cash in and out — typical for budgeting, identifying which month will hit a cash crunch, or sizing a credit facility before you actually need it. The chart makes seasonal businesses easier to plan because the lean months become visible at a glance.

If you are a startup focused on a single "how many months of runway?" number, the Burn Rate Calculator is more direct. For accounting profit (rather than bank balance), the Net Profit Calculator walks the income statement instead.

Worked example

A UK ecommerce business invoices £45,000 of revenue per month consistently. Customers pay on Net 30 terms, so the cash from January's £45,000 of invoices arrives in February. The supplier — a UK manufacturer — invoices £18,000 of stock per month on Net 0 (payment-on-delivery). Other variable costs (payment processing, shipping, packaging) total £6,000 per month, also paid in-month.

Project the first 60 days from a zero cash balance. January cash out: £18,000 supplier + £6,000 other = £24,000. January cash in: zero — invoices issued, not yet collected. End-of- January cash balance: −£24,000. February cash out: £24,000 again. February cash in: £45,000 from January's invoices. End-of-February cash: −£3,000. By end of March, with another £45,000 arriving against £24,000 of cost, the balance reaches +£18,000.

The business is profitable on paper (£21,000 of monthly gross contribution) but operationally bankrupt in week one without working-capital coverage of at least £24,000. This is the most common cause of small-business failure: profitability is not liquidity. The two highest-leverage fixes are shortening receivables (offer a 2% discount for prepayment, or move to Net 14) and lengthening payables (negotiate Net 30 with the supplier, even at a slightly higher unit price). A 30-day shift in the cash-conversion cycle frees £45,000 of working capital — usually more than the business's actual profit for the quarter.

Frequently Asked Questions

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Try these scenarios

Pre-filled examples — click any chip to load the inputs and result.

• Steady SMB: $10k opening, $12k in / $9.5k out
• Lean startup: $50k opening, $5k in / $15k out
• Scaling agency: $25k opening, $40k in / $32k out

How to project 12-month cash flow

1. 1
   Enter your opening cash balanceBank + liquid assets at the start of month 1.
2. 2
   Fill in each month's incomeEstimated revenue or cash receipts for each of the 12 months ahead.
3. 3
   Fill in each month's expensesEstimated total cash outflows — salaries, rent, software, supplier payments.
4. 4
   Read net cash flow and running balanceEach month shows net flow (green positive, red negative) and the running balance. The chart highlights any month where cash goes negative.