Cash Flow Runway Calculator

A healthy sales report does not guarantee that a business can meet its next payroll. Cash arrives when customers pay, while rent, wages, tax remittances, debt payments, and suppliers follow their own schedules. Cash runway turns those movements into a timeline, showing how long spendable operating cash can remain above zero and above a reserve chosen for safer decisions.

Runway planning starts with money that is genuinely available. Unpaid invoices are receivables rather than cash, an unapproved credit line is not funding, and amounts held for tax or another restricted purpose may not be available for operations. The forecast becomes more useful when collections are dated conservatively and recurring costs include the less visible items that still leave the bank account.

Recurring cash flow

Collected cash expected each month minus fixed, payroll, and variable cash outflows.

Net burn

The recurring shortfall when monthly cash out is greater than monthly cash in.

Safety floor

A minimum operating balance that triggers action before cash reaches zero.

Runway

The modeled time to a zero-cash crossing within the chosen forecast horizon.

Two businesses with the same monthly burn can have very different risk. A company expecting a large, reliable collection next month may have a timing gap. Another may have recurring costs that exceed collections every month, which is a structural gap. Scenario planning helps separate those cases by testing slower receivables, lower spending, faster inflow growth, and a one-time funding bridge against the same base forecast.

A reserve-floor date is often more actionable than the zero-cash date. Hiring freezes, supplier negotiations, collection work, financing, or owner decisions take time. An early warning also leaves room for normal forecast error, whereas waiting for the bank balance to approach zero can turn every response into an emergency.

This remains a planning estimate. Monthly buckets smooth over the exact day when bills clear, and a forecast can only reflect obligations and receipts that were entered. Reconcile it regularly with bank balances, receivables, payables, payroll, taxes, financing commitments, and any restrictions on cash.

How to Use This Tool:

Build the baseline from cash that is expected to clear, then use the comparison scenarios to find which assumption changes the decision date.

1. Choose a Starting profile for editable example values or select the custom plan, then keep every amount in the currency shown under Currency. The currency choice labels values but does not convert them.
2. Enter Current cash, recurring Monthly cash inflow, and the one-time Receivables due. Set Collection delay to when that receivable is reasonably expected to arrive.
3. Add Fixed outflow, Payroll outflow, and Variable outflow. Include cash costs once, in the category that best matches how they leave the account.
4. Set monthly inflow and outflow growth, the Safety cash floor, the forecast start, and a horizon from 3 to 36 months. A horizon-end result means no crossing was observed in that window, not that the runway is unlimited.
5. Use Payable timing only for agreed payment timing. Add Committed funding only when the amount and month are credible, then set the reserve-planning window used to estimate a bridge.
6. Compare the baseline with cost control, inflow upside, receivable stress, and funding bridge in Runway outlook. Check Monthly forecast to confirm that major cash events fall in the intended months.

Interpreting Results:

Runway is the first modeled zero-cash crossing. Safety floor timing is the earlier management warning, while Funding needed is the amount that would lift the lowest baseline balance through the selected reserve window back to that floor.

• A result equal to the forecast horizon means zero or the floor was not reached during the modeled months. Extend or roll the forecast before treating that value as durable.
• Net monthly cash flow excludes one-time receivables, funding, growth, and timing shifts. Use it to spot structural burn, then use the monthly rows for the full runway result.
• A sharp difference between baseline and receivable-stress paths points to collection concentration. A large improvement from cost control shows how much time the selected reduction could buy.
• A bridge amount is a modeled gap, not evidence that financing is available or sufficient for obligations omitted from the forecast.

Technical Details:

Each forecast month begins with the previous closing balance. Recurring inflow and scheduled outflow compound from their base amounts, while a receivable and committed funding enter once in their assigned months. Payable timing moves a share of scheduled outflow into the following month without reducing the scheduled amount.

Formula Core:

The balance identity below is applied month by month. Month index t begins at zero.

Receivables enter month $floor(D/30)$, capped at the final forecast month. The stress path adds the chosen delay before applying that rule. Cost control reduces every scheduled outflow by its selected percentage, and inflow upside adds percentage points to recurring monthly inflow growth.

When a balance moves from above a threshold to at or below it, crossing time is linearly interpolated inside that month.

The boundary B is either zero or the safety floor. If opening cash is already at or below the boundary, crossing time is zero. The bridge amount is the greater of zero and the difference between the safety floor and the minimum closing balance through the selected reserve window. Calculations retain full precision; compact or detailed display changes presentation only.

Limitations and Privacy Notes:

This is a cash-planning model, not an accounting statement, bank reconciliation, financing decision, or tax, legal, or investment opinion.

• Monthly buckets do not model the exact day of payroll, taxes, card settlements, debt service, or supplier payments.
• Payable timing carries a share of each scheduled outflow into the next month. The forecast does not append an extra settlement month, so a share deferred from the final month falls beyond the selected horizon.
• Growth rates compound without seasonality unless the entered assumptions approximate it. Large one-time events beyond the single receivable and funding entries need to be reflected in the recurring inputs or modeled separately.
• The forecast does not check invoice quality, restricted cash, covenants, overdrafts, exchange rates, or access to funding.
• Cash values are calculated in the browser. Copied tables, downloaded files, or shared URLs can disclose sensitive business assumptions, so handle them as financial records.

Worked Examples:

References:

• Managing Cash Flow, Money Smart for Small Business Module 10, Federal Deposit Insurance Corporation and U.S. Small Business Administration, 2026.
• Publication 583, Starting a Business and Keeping Records, Internal Revenue Service.