Cash Runway: How to Calculate It and How to Extend It

Cash runway is the number of months a company can keep operating before it runs out of cash. The simple version divides the cash balance by the current monthly net burn. The accurate version subtracts the projected burn month by month, because costs and receipts rarely stay flat. Runway turns a cash balance into a deadline, which is why founders, boards and lenders ask for it first. This guide shows both calculations, a worked example of extending runway with specific actions and the decisions that follow. It builds on burn rate and supports cash flow management.

The simple formula

Runway (months) = Cash balance / Net burn per month

With $960,000 in the bank and a net burn of $80,000, runway is 12 months. This is a quick check and a useful starting point. It assumes burn will stay exactly where it is, which is rarely true.

The forward-looking calculation

Build a month-by-month projection of net burn and subtract it from the cash balance until the balance reaches zero.

Suppose burn is $80,000 in month 1 and rises by $5,000 each month as the company hires.

After nine months, $60,000 remains, and month 10 needs $125,000. Runway is 9 months plus $60,000 / $125,000 = 0.48 of a month, or about 9.5 months, compared with the 12 months of the simple formula. The difference is the cost of the planned growth in spending.

Make the projection realistic

The accuracy of runway depends on the quality of the inputs.

• Receipts. Use realistic collection timing, not invoice dates. See how to build a cash flow forecast you will actually use.
• Hiring. Include start dates, loaded costs, recruiting fees and equipment.
• One-time and annual items. Insurance renewals, annual software payments, taxes and bonuses create spikes.
• Working capital. Growth in receivables and inventory consumes cash before profit arrives.
• Debt service. Include principal and interest, and any balloon payments.
• Contingency. Add a margin for the unexpected.

Build at least three cases: base, downside and a cost-control case. See cash flow scenario planning. Present runway for each, and decide which one to use for decisions. Many boards focus on the downside case.

What counts as cash

Decide and state what is included.

• Cash and equivalents in the bank: included.
• Undrawn committed credit: often shown separately as "liquidity", since lenders may restrict access.
• Receivables: not cash until collected; reflected through the forecast.
• Restricted cash and customer deposits: exclude amounts you cannot spend.
• Committed but not yet funded investment: include only when the money is received, or show it as a separate scenario.

How sensitive is runway?

Runway moves quickly with burn. With $960,000 of cash and a flat burn, the simple formula gives:

A $10,000 change in monthly burn moves runway by between 1.1 and 1.7 months in this range. This is why small, lasting cost reductions are valuable and why a rising burn deserves attention early. If you see runway shrinking despite flat cash, read cash flow problems: 10 early warning signs to find the cause.

Runway also depends on timing of receipts. A single large customer paying one month late can remove a month of the cushion, even if burn is unchanged. Test the effect in your forecast.

Extending runway: a worked plan

Return to the example. The company has $960,000 and the baseline path above, giving 9.5 months. Management proposes four actions:

1. Cut marketing by $10,000 a month starting in month 3.
2. Freeze hiring after month 3, holding gross burn at the month 3 level instead of rising by $5,000 a month.
3. Collect $60,000 of overdue receivables in month 2.
4. Negotiate 15 more days of terms with suppliers in month 3, releasing a one-time $12,000.

The revised net burn is:

Cumulative burn under the plan: month 1, $80,000; month 2, $105,000; month 3, $173,000; then $80,000 a month, so $253,000 after month 4, and $893,000 after month 12. Cash of $960,000 leaves $67,000 after month 12, enough for a further $67,000 / $80,000 = 0.84 of a month. Runway under the plan is about 12.8 months, compared with 9.5 months. The four actions add roughly 3.3 months.

Notice the sources of the gain. The hiring freeze and marketing cut produce a lasting reduction in burn. The collections and terms actions are one-time and shift cash earlier. Do not count one-time gains as if they would recur.

Levers to extend runway

Reading the plan critically

Before relying on a runway extension plan, test each action.

• Is the saving real? A hiring freeze saves money only if the hires were in the baseline. Check against the budget.
• Is it lasting or one-time? The marketing cut and freeze recur; the collections and terms gains do not.
• What does it cost elsewhere? Cutting marketing may lower receipts in later months. Estimate the effect and include it.
• When does the cash arrive? A negotiated change in terms may take a month or more.
• Who owns it? Each action needs a person and a date.

If the plan is credible, share it with investors or lenders. A realistic plan with owners builds confidence. An optimistic one that misses will cost credibility.

When to act

The best time to extend runway is long before you need to. Cost cuts take time to take effect, and fundraising or lending takes months. A common approach is to set trigger points tied to months of runway, for example:

The numbers are examples. Your own thresholds should reflect how long it takes to raise money in your market, your ability to cut costs quickly and the severity of the downside.

Runway and fundraising

Investors and lenders will test your runway. Be ready with:

• A monthly forecast for at least 18 months
• The assumptions behind revenue and costs
• Base, downside and cost-control cases
• Clear milestones the new money will fund
• A record of forecast accuracy. See how to measure and improve cash forecast accuracy

A company that raises with a long runway negotiates from strength. One that raises with a short runway may accept worse terms or fail to close. See cash flow forecasting for startups for what investors look for.

Runway for established companies

Runway is not only a startup concept. A profitable company can still face a cash squeeze if working capital absorbs the profit. Established companies can use runway thinking for downturns: how many months can we operate if sales fall 20 percent and customers pay late? Product companies should include inventory commitments, since purchase orders can lock in cash outflows. The link between demand planning and cash is covered in demand planning and inventory optimization.

Common mistakes

• Dividing cash by today's burn when burn is rising.
• Counting one-time gains as lasting.
• Ignoring working capital growth.
• Using only one scenario.
• Waiting too long to act.
• Counting committed credit as cash without checking terms.
• Not updating the projection each month.

FAQs

What is cash runway?

It is the number of months a company can continue operating before running out of cash, based on its cash balance and projected burn.

How do you calculate cash runway?

Divide cash by monthly net burn for a quick estimate. For accuracy, subtract projected burn month by month until the balance reaches zero.

How much runway should a company have?

There is no single answer. Many companies aim to start raising or restructuring with a meaningful buffer, because both take time. Choose thresholds based on how long raising takes, your cost flexibility and your downside case.

How can I extend my runway?

Reduce costs, slow hiring, collect receivables, extend supplier terms, cut inventory, improve pricing, defer capital spending or raise financing. Separate lasting gains from one-time ones.

Does runway include receivables?

Not directly. Receivables become cash when collected, so reflect them through the timing of expected receipts in the forecast.