Cash Runway Calculator — How Many Months of Cash Are Left

Background.

How long will the money last? With $4.8 million in the bank and $160,000 going out each month after customer receipts, simple division says 30 months. If the operating plan adds 3% to that burn every month, as a steady hiring schedule might, the cash is gone in 21.71 months. The extra spending does not shorten runway at the start, when it is still small; it takes the months from the end, which is exactly where the next fundraise was supposed to happen.

Runway is a stock divided by a flow: the cash you are prepared to spend, divided by the net amount the business consumes each month. Both halves need care. The stock is unrestricted cash actually in the account, less any reserve you have set aside to close the company in an orderly way should it come to that. The flow is net burn, cash out minus cash collected from customers, averaged over a few months so that one quarterly bill or one large renewal does not swing the answer by a season.

Allow burn to grow or shrink at a steady monthly rate and you get the compounding answer next to the flat one, the months that separate them, and how large the monthly burn has become by the time the cash is spent. A status line then says whether the result falls inside or beyond 12 months, the horizon that US going-concern accounting and SEC liquidity disclosure both use.

What is cash runway calculator?

Cash runway is the number of months a company can keep operating before its spendable cash runs out, given how much cash it consumes each month. Spendable cash is unrestricted cash and cash equivalents, less any reserve deliberately held back. Net monthly burn is the cash consumed each month after customer collections, the amount by which the bank balance actually falls. Runway is a planning measure rather than an accounting one: it appears in no financial statement, no standard-setter defines it, and two companies can compute it differently in good faith, which is why the cash definition, the averaging period and any growth assumption should travel with the number. For a startup it sets the calendar for hiring, cost decisions and the next raise.

How to use this calculator.

1. 01Enter cash on hand as unrestricted cash and cash equivalents in the account today. Leave out restricted cash, undrawn credit lines and money promised under a signed but unfunded term sheet.
2. 02Enter net monthly burn as a positive number: cash out minus cash collected from customers, averaged over the last three months. If you only have expense figures, work it out first with the burn rate calculator.
3. 03Set the monthly change in burn. Use 0 for a flat plan, a positive percentage when hiring or usage-driven costs are scheduled to rise, and a negative one only for cuts that have already taken effect.
4. 04Set a reserve floor if you hold back cash for an orderly wind-down: final payroll, notice periods, severance, lease obligations and closing legal and accounting fees. Runway is then measured to that floor instead of to zero.
5. 05Compare runway with the flat-burn figure and read the months lost, then look at the burn in the final month to see how far the plan moves the cost base from where it is today.
6. 06Plan backwards from the result: subtract the months a raise is likely to take and the cushion you want left when it closes, and the remainder is roughly when the process has to start.

The formula.

With flat burn, runway is n = S ⁄ B, where S is spendable cash (cash on hand minus the reserve floor) and B is today's net monthly burn.

When burn changes by a fixed fraction g each month, month i costs B(1 + g)^(i − 1), so the months form a geometric series. The total spent over n months is B × ((1 + g)^n − 1) ⁄ g. Setting that equal to S and solving for n gives n = ln(1 + S·g ⁄ B) ⁄ ln(1 + g). The answer comes out as a continuous number of months: 21.71 means 21 full months plus about 71% of the 22nd. On the default inputs, 21 full months consume $4,588,237.72, leaving $211,762.28 against a 22nd-month burn of $297,647.13, which covers 0.71 of it.

The burn in the final month is B(1 + g)^(n − 1). Because (1 + g)^n equals 1 + S·g ⁄ B at the end of runway, this simplifies to (B + S·g) ⁄ (1 + g), a quick hand check: (160,000 + 144,000) ⁄ 1.03 = $295,145.63.

The growth rate is the input to be careful with, because its effect compounds. On $4.8 million and $160,000 of burn, runway is 30 months at 0%, 26.37 at 1% a month, 21.71 at 3%, 18.78 at 5% and 14.55 at 10%. The monthly change can be set anywhere from −50% to 100%.

A shrinking burn behaves differently. With g negative, the total that will ever be spent converges to B ⁄ |g|, and if that is no more than S the cash is never exhausted; the condition is g ≤ −B ⁄ S. For the default inputs that is a cut of 3.33% or more every month. Such cases, and any answer past 600 months, are reported as 600 months with the status line saying the cash is not exhausted within the model's 50-year horizon.

The model's main limitation is that one constant rate is a smooth curve, while real burn moves in steps when a hiring wave lands, a contract renews or a layoff takes effect. Revenue enters only through net burn, so faster or slower collections show up as a different B or g, not as a separate input.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Financial Accounting Standards Board (August 2014). Accounting Standards Update No. 2014-15, "Presentation of Financial Statements — Going Concern (Subtopic 205-40)." Source for the one-year-after-issuance substantial-doubt evaluation performed each annual and interim period. Authoritative PDF; URL verified live 29 July 2026 (binary PDF — text cross-checked against PwC Viewpoint's ASC 205-40 chapter, which is an independent reading of the same standard).
2. [2]17 CFR § 229.303(b)(1) (Regulation S-K Item 303, as amended by SEC Release 33-10890). Quoted verbatim on this page: liquidity and capital resources must be described "short-term (i.e., the next 12 months from the most recent fiscal period end required to be presented) and separately in the long-term (i.e., beyond the next 12 months)". Text fetched and verified 29 July 2026 via the Cornell LII mirror of the eCFR; sec.gov itself returns HTTP 403 to automated fetchers but is browser-accessible.
3. [3]Graham, P. (October 2015). "Default Alive or Default Dead?" Source for the default-alive / default-dead framing and for the argument that founders should ask the question early. Retrieved 29 July 2026.
4. [4]Jordan, J., Hariharan, A., Chen, F., & Kasireddy, P. (21 August 2015). "16 Startup Metrics." Andreessen Horowitz. Source for the gross-burn and net-burn definitions that determine which figure belongs in the denominator here. Retrieved 29 July 2026; quotes verified verbatim.
5. [5]Sacks, D. (23 April 2020). "The Burn Multiple." Craft Ventures. Consulted as an independent second authority on the sign and meaning of net burn — the burn multiple (net burn ÷ net new ARR) is only interpretable when net burn is stated as a positive number of dollars consumed, the convention used here. Retrieved 29 July 2026.
6. [6]U.S. Securities and Exchange Commission (30 January 2020). Release No. 33-10751, "Commission Guidance on Management's Discussion and Analysis of Financial Condition and Results of Operations" — requires a registrant presenting a metric such as runway or burn to disclose its definition and method of calculation. Effective 25 February 2020. sec.gov blocks automated fetchers (HTTP 403); release number, title and dates verified independently.