Cash Flow Projection Calculator
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Model your cash position month by month: set a starting balance, add recurring inflows and outflows, then override any month to see the running balance, ending balance and lowest cash point.
What a cash flow projection actually shows
A cash flow projection is a forward-looking view of your bank balance, not your profit. It starts from the cash you hold today and walks forward month by month, adding everything you expect to collect and subtracting everything you expect to pay. The output that matters is the running balance: the closing figure at the end of each month, carried into the next.
This distinction trips up many owners. A business can be profitable on paper and still fail because it runs out of cash between the moment it pays suppliers and the moment customers settle their invoices. Profit is an accounting concept measured over a period; cash is a timing concept measured at a point. A projection makes the timing visible.
- Starting balance: the cash you hold at the beginning of month one.
- Inflows: sales receipts, deposits, loans, tax refunds, owner contributions.
- Outflows: payroll, rent, supplier bills, loan repayments, tax, one-off purchases.
- Running balance: previous close plus inflows minus outflows, for each month.
The formula behind the running balance
The maths is deliberately simple, which is what makes it reliable. For month one, the closing balance equals the starting balance plus that month's inflows minus its outflows. For every month after that, you replace the starting balance with the previous month's closing balance and repeat.
Written out, closing[n] = closing[n-1] + inflow[n] − outflow[n], with closing[0] set to your opening balance. The tool applies this recurrence across every month you project, so a change in one month ripples through all the later months automatically. Total inflow and total outflow are just the sums of each column across the whole horizon.
Reading the ending balance versus the lowest balance
Two numbers deserve your attention. The ending balance tells you where you land at the end of the projection, and the lowest balance tells you the tightest point you pass through on the way. The lowest balance is often the more important of the two.
Consider a consultancy that invoices a large project in month one but is not paid until month four, while payroll goes out every month. The ending balance might look healthy, yet the lowest balance could dip below zero in month three. That dip is a warning: you need a cash buffer, an overdraft, or to renegotiate payment terms before it happens. A negative lowest balance shown in red on the chart is the single most useful signal this tool produces.
When to use it and where it falls short
Use a projection when you are planning hiring, taking on a loan, buying equipment, or entering a seasonal slow period. Rebuild it whenever reality diverges from the plan, and treat the recurring figures as a baseline you override with the specific bills and receipts you actually expect.
The projection is only as good as its assumptions. It does not know that a customer will pay late, that a tax bill is due, or that revenue is seasonal unless you tell it by editing the relevant month. It also ignores non-cash items like depreciation, and it does not model interest on negative balances. Treat it as a planning aid to pressure-test decisions, not as a guarantee, and revisit it monthly.
Frequently asked questions
Does this replace a profit and loss statement?
No. A profit and loss statement measures earnings over a period and includes non-cash items like depreciation. A cash flow projection tracks the actual money in your bank account over time. A business can be profitable yet still run short of cash, which is exactly what this tool is designed to catch.
How many months should I project?
Twelve months is a common planning horizon, but three to six months gives a sharper, more accurate view because near-term figures are easier to estimate. Longer horizons are useful for spotting seasonal dips, though the later months become guesses. The tool supports up to 120 months.
How do I model a one-off cost like a tax bill or new equipment?
Set your recurring inflow and outflow first so the table pre-fills a baseline, then click into the specific month's outflow cell and add the one-off amount, or replace the recurring figure entirely. The running balance and chart update instantly and carry the effect through every later month.
What does a negative lowest balance mean?
It means that at some point in your projection your account is forecast to go below zero, so you would need an overdraft, a loan, or a delay in payments to keep operating. The tool highlights this point in red so you can act before it happens rather than after.
Can I change the currency?
Yes. Enter any symbol you like in the currency field, such as $, EUR, or a three-character code. It is used purely for display in the table, statistics, and chart, and does not affect the calculations.
Is my financial data private?
Yes. Every calculation runs in your browser using JavaScript. Nothing you type is sent to a server, stored, or uploaded, so you can model sensitive figures without them ever leaving your device.
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