Cash Flow Forecast Calculator
Project your cash balance month by month. Enter your starting cash, expected income and expenses, and see your closing balance for each of the next few months — plus your projected end balance and how many months of runway you have before cash runs out.
- Net monthly cash flow0
- Runway—
| Month | Opening | In | Out | Closing |
|---|
How to forecast your cash flow
A cash flow forecast is simply a running balance: take the cash you have today, add what you expect to collect, subtract what you expect to spend, and carry the result forward month after month. The value isn't the exact figure — it's seeing which month turns red before it actually happens, so you have time to react.
- Closing stays positive: you're covered across the horizon.
- Net monthly flow positive: cash-flow positive — the balance keeps building.
- Net monthly flow negative: you're burning cash; the runway line shows how long it lasts.
Cash runway: how long your money lasts
Runway is the number of months your current cash will cover a recurring shortfall. When your net monthly cash flow is negative, runway is roughly starting cash ÷ monthly burn — the point at which the closing balance hits zero. A short runway is an early warning: it gives you weeks or months to raise prices, trim costs, line up financing or accelerate collections before the account actually empties. If your net monthly flow is positive, you have no runway limit and the balance compounds upward instead.
Why overdue receivables wreck the forecast
A forecast is only as good as its timing. Money you have invoiced but not yet collected is not cash — it only helps the month it actually lands. When customers pay late, that inflow slides into a later month and can flip an otherwise healthy month negative, even while your profit-and-loss looks fine. This is why days sales outstanding (DSO) is the single biggest lever on most small-business forecasts: every day you shave off collection time pulls cash forward and lifts every closing balance after it.
The biggest swing factor for most small businesses is money already invoiced but not yet collected. Tighten that up with our cash flow tips for small businesses and learn how to reduce DSO so the income in your forecast actually arrives on time.
Related tools
- DSO Calculator — measure how fast you collect cash.
- Late Fee Calculator — work out interest and fees on overdue invoices.
FAQ
What is a cash flow forecast?
A cash flow forecast projects how much cash you will have at the end of each future month. You start with your current cash balance, add expected income (money coming in) and subtract expected expenses (money going out) to get a running closing balance.
Why does a cash flow forecast matter?
It tells you whether you can cover payroll, rent and suppliers in the months ahead. Spotting a negative month early gives you time to cut costs, raise prices, delay spending or chase money owed to you before you actually run out of cash.
How do unpaid invoices affect my forecast?
Money you have invoiced but not yet collected is not cash — it only helps your forecast in the month it actually lands. Late-paying customers push that income further out, which can turn an otherwise healthy month negative. That is why collecting receivables on time is the single biggest lever on most small-business forecasts.
What is cash runway?
Runway is how many months your cash will last if your net monthly cash flow stays negative. If you burn more than you bring in each month, runway = starting cash ÷ monthly burn. If your net monthly cash flow is positive, you are cash-flow positive and have no runway limit.
Is this calculator free and private?
Yes. It is completely free with no sign-up, and every calculation runs entirely in your browser. None of the numbers you enter are sent to a server or stored anywhere.