Cash Flow Forecast Calculator

This cash flow forecast calculator builds a simple month-by-month view of a business bank balance. Start with the cash you have now, add expected revenue, then subtract fixed costs, variable costs, and other regular cash outflows.

It is meant for the kind of planning that happens before a decision, not after the bank balance has already become uncomfortable. A founder might use it before hiring. An agency might use it before taking on a retainer with slow payment terms. A shop might use it before ordering stock for a busier season.

Profit and cash flow are related, but they are not interchangeable. Profit can look fine while cash is tight because customers pay late, stock is bought early, tax is due in a lump, or payroll lands before invoices clear. This page focuses on the cash question: what could be left in the bank at the end of each month?

Use it when a static burn rate calculator or startup runway calculator is too blunt. If revenue is changing, costs rise with sales, or you want to test a decision before committing cash, a month-by-month forecast gives you a better conversation with yourself.

Imagine a small agency has £25,000 in the bank. It invoices about £18,000 per month and expects revenue to grow by 3% per month. Fixed costs are £12,000, variable delivery costs are 35% of revenue, and another £1,500 leaves the business each month for drawings, tools, loan payments, and tax set-asides.

On paper, that can feel manageable. The forecast is more useful because it shows the dip before the recovery. In the default example, cash falls for several months before the growing revenue base catches up. That low point matters more than the final month, because the business has to survive the dip before it gets to the nicer number at the end.

This is the moment to test the hire. If fixed costs rise by another £3,500 for salary, software, payroll costs, or contractor cover, the same forecast can change from comfortable to tight. The question is not just whether the hire should pay back eventually. It is whether the business has enough cash to carry the decision while that payback arrives.

A product business can be profitable and still feel short of cash. Suppose a shop expects a strong quarter and orders extra inventory before the sales arrive. The profit margin may be healthy, but the cash leaves first: stock deposits, shipping, card fees, packaging, temporary staff, and advertising can all land before customers pay.

A service business has a different version of the same problem. The work is delivered this month, the invoice is raised next month, and the client pays 30 or 45 days later. The revenue forecast scenario calculator can show the top-line sales plan, but this calculator keeps attention on the bank balance while that revenue is turning into cash.

If the forecast only works when every invoice lands on time and every cost stays flat, it is not really a forecast yet. A stronger version includes a cautious case: slower growth, higher variable costs, or a larger other-cash-out figure to allow for late payments, refunds, tax timing, or one awkward supplier bill.

Starting cash is the available bank balance at the start of the forecast. Monthly revenue is the first month's expected income. Revenue growth is applied each month, so a positive growth rate compounds through the forecast rather than adding the same amount every time.

Fixed costs are the bills that stay broadly stable: payroll, rent, software, insurance, retainers, minimum contractor commitments, accountancy, and core overhead. Variable cost percentage covers costs that rise with revenue, such as card fees, materials, commissions, fulfilment, hosting usage, packaging, or delivery labour.

Other monthly cash out is deliberately plain. Use it for recurring cash payments that do not fit neatly into fixed or variable costs: loan payments, owner drawings, equipment finance, tax reserves, planned stock purchases, professional fees, or a regular buffer for messy real-world costs.

For margin checks, pair the forecast with the net profit calculator. For survival timing, compare it with the startup runway calculator. Cash flow, profit, and runway answer different questions, and most business decisions need at least two of the three.

A cash flow forecast is most useful when you run more than one scenario. Start with the base case you genuinely expect, not the version that makes the decision look easy. Then run a cautious case with slower sales, higher costs, or a delayed payment pattern.

A decision case is often the most revealing. Increase fixed costs to represent a new hire, raise other cash out for a stock order, or lift variable costs to model a supplier price increase. If the lowest cash point still looks safe, the decision is easier to defend.

The forecast should also tell you what to watch. If cash gets tight in month four, month one is the time to chase deposits, shorten payment terms, delay discretionary spend, or arrange funding. The point is not to predict the future perfectly. The point is to see the pressure early enough to act.

For wider context, the small business finance and growth guide explains how cash flow sits alongside margin, break-even, ROI, CAC, churn, and pricing. Cash is one part of the model, but it is usually the part that gives the least warning when it starts going wrong.

This calculator is intentionally simpler than accounting software. It does not model individual invoices, payment terms, VAT or sales tax timing, payroll taxes, inventory purchases, deferred revenue, debt schedules, grants, fundraising, or one-off capital expenditure.

For a serious business decision, compare the forecast with bank statements, debtor reports, creditor reports, tax liabilities, payroll commitments, and actual accounting records. If timing differences matter, build a more detailed spreadsheet from expected receipt dates and payment dates.

Treat the output as a planning signal. If the forecast shows cash falling toward zero, the next step is not panic. It is choosing the lever that matters most: faster collections, lower costs, different payment terms, a price change, funding, or delaying the commitment until the low point is safer.

Cash flow forecasting is not about making a spreadsheet look clever. It is about catching the boring, dangerous timing gaps before they become urgent.