Cash Flow Forecast Calculator

Project your cash balance over time from starting cash, monthly inflows and outflows, and growth rates. See your runway and month-by-month cash flow chart.

What is Cash Flow Forecast Calculator?

A cash flow forecast projects how a business's cash balance will change over time, based on expected monthly inflows (revenue, collections) and outflows (expenses, payroll, rent, debt payments). Unlike profit, which can be recognized before cash actually changes hands, a cash flow forecast tracks the literal timing of money moving in and out of a bank account — the number that ultimately determines whether bills get paid.

This is especially critical for startups and small businesses that don't yet have steady positive cash flow. Running out of cash, not running out of profitability, is one of the most common reasons businesses fail — many profitable-on-paper companies have collapsed because they couldn't cover payroll or rent during a cash crunch.

This calculator projects a cash balance forward from a starting amount, given expected monthly inflows and outflows (with optional growth rates for each), and calculates the runway — the point at which cash would run out if nothing changes. Seeing this number early gives a business time to act: cut costs, accelerate collections, or raise financing before the situation becomes urgent.

Formula

Inflow(month) = Monthly Inflow × (1 + Inflow Growth %)^(month - 1)

Outflow(month) = Monthly Outflow × (1 + Outflow Growth %)^(month - 1)

Net Cash Flow(month) = Inflow(month) - Outflow(month)

Balance(month) = Balance(month - 1) + Net Cash Flow(month)

Runway = first month where Balance ≤ 0

Example: Starting cash $50,000, inflow $8,000/mo, outflow $12,000/mo, no growth

Net burn = -$4,000/mo → Runway ≈ 12.5 months

How to Calculate

Enter your current starting cash balance.
Enter expected monthly cash inflow (revenue, collections).
Enter expected monthly cash outflow (expenses, payroll, rent).
Enter the number of months to project forward.
Optionally enter monthly growth rates for inflow and outflow, then review the balance chart and runway.

Example

A startup has $150,000 in the bank, brings in $20,000/month in revenue (growing 5% monthly), and spends $35,000/month on expenses (growing 2% monthly). The forecast shows the cash balance declining each month despite inflow growth, with runway hitting zero around month 9 — giving the founders roughly 9 months to raise financing, cut costs, or grow revenue faster.

Key Benefits

See your projected runway before cash actually becomes a problem
Model how changes in revenue or spending growth affect your cash position over time
Communicate cash position clearly to investors, lenders, or co-founders
Plan hiring, purchasing, or expansion decisions around actual cash availability, not just profit
Catch a looming cash shortfall months in advance, when more options are available to address it

Common Mistakes to Avoid

Confusing profit with cash — assuming a profitable month means cash is also growing
Basing inflow projections on optimistic best-case revenue rather than realistic historical trends
Forgetting to include irregular but predictable outflows like annual insurance or tax payments
Not updating the forecast regularly, so it drifts further from reality each month
Waiting until cash is critically low to act, instead of addressing a projected shortfall months in advance

Pro Tips

Base your inflow and outflow assumptions on actual historical averages, not hopeful projections.
Build a cash buffer into your outflow assumptions for unexpected expenses.
Update your forecast monthly with actual results to keep the projection grounded in reality.
Model a conservative scenario alongside your expected case to see your worst-case runway.
If your runway is shortening, address it early — accelerating collections or cutting costs is far easier with months of lead time than weeks.

Key Terms Explained

Cash Flow: The actual movement of cash into and out of a business, distinct from accounting profit
Runway: The number of months a business can operate before running out of cash at current burn rate
Burn Rate: The rate at which a business spends down its cash reserves each month
Inflow: Cash coming into the business, primarily from revenue and customer collections
Outflow: Cash leaving the business, including expenses, payroll, rent, and debt payments

Common Use Cases

Startup founders tracking runway before their next funding round
Small business owners planning for seasonal revenue dips without running out of cash
Finance teams building monthly cash forecasts for board or investor reporting
Business owners deciding whether they can afford a new hire or major purchase
Anyone modeling the cash impact of a planned expense increase or revenue slowdown

Frequently Asked Questions

What is a cash flow forecast?

A cash flow forecast projects how much cash a business will have at future points in time, based on expected incoming cash (revenue, receivables) and outgoing cash (expenses, payroll, rent). Unlike a profit-and-loss statement, it focuses purely on cash timing, which is what determines whether a business can pay its bills.

What is runway?

Runway is the number of months a business can continue operating before running out of cash, assuming current inflows and outflows continue. If a company has $100,000 in cash and burns $10,000 net per month, its runway is 10 months. Runway is one of the most important numbers for any business without positive cash flow, especially startups.

Why forecast cash flow instead of just tracking profit?

A business can be profitable on paper but still run out of cash — for example, if customers pay slowly (accounts receivable) or if there's heavy upfront investment in inventory or equipment. Cash flow forecasting tracks actual cash timing, which determines whether bills, payroll, and debts can actually be paid when due.

How do I improve my cash flow forecast?

Improve accuracy by basing inflow and outflow estimates on historical data rather than optimistic projections, building in a buffer for unexpected expenses, updating the forecast monthly as actual results come in, and modeling multiple scenarios (best case, worst case, expected case) rather than a single number.

What should I do if my forecast shows I'll run out of cash?

If your forecast shows a cash shortfall, act early: reduce discretionary spending, accelerate collections from customers, negotiate extended payment terms with suppliers, delay non-essential hires or purchases, or raise additional financing. Acting months before the shortfall, rather than when cash is already critically low, gives you far more options.

How often should a business update its cash flow forecast?

Most small businesses and startups benefit from updating their cash flow forecast monthly, replacing projected figures with actual results as they come in and extending the projection horizon forward. Businesses with tighter cash positions or higher volatility may benefit from weekly updates.