Runway Calculator

Business runway calculator for cash burn and months of runway

A runway calculator estimates how long your business can keep operating before it runs out of cash, assuming your current monthly revenue and monthly operating expenses stay roughly consistent. The main decision this supports is simple: “How many months do I have before I must cut costs, grow revenue, or raise funding?” This page is locked to that use case: short-term cash runway for a business based on ongoing monthly inflows and outflows.

To use it, start with the quick inputs: cash on hand, average monthly revenue, and average monthly operating expenses. The calculator converts these into a monthly net burn (expenses minus revenue). If your burn is positive, your cash balance shrinks each month and the calculator estimates your runway in months and the approximate month when you hit your minimum cash reserve. If your burn is zero or negative, your cash is stable or growing, and your runway is effectively not constrained by cash at the current levels.

The advanced section is optional and is only there to improve realism when you have it. Monthly growth rates let you model a business where revenue is increasing (or decreasing) over time, and expenses are drifting upward. One-time cash injections and one-time planned costs are applied in month one to reflect a funding drawdown, a grant, a large invoice, an equipment purchase, or a once-off tax payment. The minimum cash reserve input lets you keep a safety buffer by defining the point where you stop counting runway, rather than waiting for cash to hit absolute zero.

Assumptions and how to use this calculator

• Runway is based on average monthly figures, not daily timing. If cash timing matters (payroll dates, large invoices), treat the result as a planning estimate, not a bank-balance forecast.
• Monthly revenue and expenses are assumed to recur each month. One-time events should be entered in the advanced section to avoid overstating or understating runway.
• Growth rates, if used, are applied monthly to revenue and expenses. A “3% monthly revenue growth” compounds month to month, which can change runway meaningfully over time.
• Minimum cash reserve is treated as untouchable. Runway ends when projected cash falls to that reserve, not when it hits zero.
• This calculator ignores financing mechanics like credit lines, loan repayments, VAT timing, and receivables aging unless you roll them into your monthly revenue and expense averages.

Common questions

What is “net burn” and why does it matter?

Net burn is your monthly operating expenses minus your monthly revenue. If it is positive, you are burning cash and runway is limited. If it is zero, cash is stable. If it is negative, you have a monthly surplus and cash grows. Net burn is the single strongest driver of runway.

Should I enter revenue as invoices issued or cash received?

Use cash received if you want runway to reflect real liquidity. If you only know invoices issued, adjust the number to reflect typical collections, or keep it simple and treat the output as a directional estimate. For businesses with long payment terms, using invoices issued can overstate runway.

My runway looks huge or “indefinite.” Is that realistic?

If revenue is equal to or higher than expenses, the calculator will show that cash does not run out under the current levels. That can be true, but it can also be misleading if you have hidden cash drains (tax, debt service, large quarterly costs) that are not in your monthly expense number. If those exist, include them by increasing monthly expenses or adding a month-one planned cost.

How do I improve accuracy without overcomplicating it?

Use a 3 to 6 month average for revenue and expenses, not your best month. Add only the big one-time items that could change the decision, like a known equipment purchase, a tax payment, or a funding injection. If you expect growth or contraction, add a modest monthly growth rate rather than trying to predict every month.

When should I stop using a runway estimate and switch to a cash flow forecast?

If your business has large timing swings (payroll weekly, sales seasonal, suppliers on strict terms), a monthly average can hide the month you actually run out of cash. In that case, runway is still useful for a fast read, but you should also build a weekly or bi-weekly forecast to manage the timing risk.