Runway

What is runway?

Runway (also called cash runway, months of runway, or time-to-zero) is the number of months a company can continue operating at its current burn rate before exhausting its cash reserves. It is calculated by dividing total cash on hand by monthly net burn. Runway is the single most consequential metric for any pre-profitability company — it sets the outer boundary of every strategic decision.

Runway is sometimes confused with cash runway, which refers specifically to a static calculation using current burn with no adjustments for growth or revenue change. True runway projections account for burn evolution — if headcount is growing, burn will increase; if revenue is growing, net burn will decrease. A static runway calculation using today's net burn on a company growing 15% MoM understates actual runway. A static calculation on a company whose revenue is declining overstates it. The distinction between static and dynamic runway matters for any company where burn or revenue is moving significantly.

The fundraise timeline creates a critical urgency threshold. A Series B fundraise from first pitch to cash-in-bank typically takes 4-6 months. A Series A takes 3-5 months. Adding 1-2 months for pre-process preparation, a company with 12 months of runway has roughly 5-7 months of actual decision-making time before the process becomes urgent. The 18-month threshold exists because it provides exactly the right buffer: start raising at 18 months, close in 5-6 months, cash arrives at 12-13 months, leaving 5-7 months of cushion if the round takes longer than planned.

For the ICP this page serves — venture-backed SaaS founders and CFOs managing fundraise timing — runway is not a metric to check quarterly. It is a metric to monitor monthly, project forward 6-12 months under multiple scenarios, and act on before it becomes a constraint rather than a parameter.

Why runway matters for operators

The cost of insufficient runway is not just financial — it is strategic. A company that initiates a fundraise with 18 months of runway can afford to say no to a term sheet that undervalues the business. A company that initiates with 5 months cannot. Runway is negotiating leverage. Every month of runway below 18 represents a reduction in the founder's ability to accept only the right deal at the right terms.

Runway also determines product and hiring roadmap feasibility. A 24-month runway supports a 12-month product build with 6 months of market testing and 6 months of fundraise. A 10-month runway forces a choice between product investment and go-to-market — not because the business is failing, but because the cash constraint has become the binding constraint on strategy. Tracking net burn and runway monthly allows operators to make these tradeoffs proactively, before they become reactive emergencies.

For CFOs specifically, runway projections are not static calculations — they are scenario models. The relevant question is not "how many months of runway do we have today?" but rather "how does runway change if we add 3 engineers, if a large customer churns, if paid media underperforms by 30%, or if the fundraise takes 3 months longer than planned?" Fairview's Forecast Confidence Engine is built specifically to answer these scenario questions with connected financial data rather than manual spreadsheet modeling.

Runway formula

Runway (months) = Total Cash ÷ Monthly Net Burn

Example:
  Cash on hand:      $2,760,000
  Monthly net burn:  $172,500
  Runway:            $2,760,000 / $172,500 = 16.0 months

Dynamic runway (accounts for revenue growth):
  Month 1 net burn:  $172,500 (current)
  MRR growth rate:   8% per month
  Projected runway:  ~20 months (burn decreasing as revenue grows)

Stress-tested runway (worst case):
  Use gross burn instead of net burn:
  Gross burn:        $240,000
  Runway floor:      $2,760,000 / $240,000 = 11.5 months

• Total cash — unrestricted cash in bank accounts; exclude receivables until collected
• Monthly net burn — gross burn minus cash revenue collected; use 3-month rolling average for stability
• Do not include unfunded commitments — signed term sheets that haven't closed are not cash
• Do not net out credit lines unless they are drawn and available; undrawn credit is not cash
• Report static runway alongside dynamic runway — both matter for different audiences
• Update monthly — runway is a leading indicator; stale calculations create false security

Runway benchmarks by funding stage

Runway is most meaningful in the context of the next fundraise. The critical thresholds below are designed around typical fundraise timelines for venture-backed B2B SaaS companies.

Sources: Y Combinator default advice on fundraise timing; a16z guidance on runway management; First Round Capital founder resources. Timelines assume venture-backed B2B SaaS. Bootstrap companies and companies with near-term profitability paths have different thresholds.

Common mistakes when calculating runway

1. Using current net burn without modeling burn evolution

A company adding 4 engineers this quarter will see gross burn increase by $60-100K/month starting next quarter. Using today's net burn to calculate runway ignores this committed future spend. Build a 12-month burn forecast that reflects the actual hiring plan, marketing commitments, and infrastructure roadmap — not just the current month's burn rate.

2. Counting unfunded receivables as cash

Signed contracts, outstanding invoices, and verbal commitments are not cash. Runway is calculated on cash in the bank. A company with $800K in cash and $400K in aged receivables has $800K of runway-eligible cash, not $1.2M. Receivables can be factored or collected, but until they clear the bank they cannot be counted. Including them creates an optimistic runway number that can collapse without warning.

3. Not accounting for seasonal revenue patterns

Many B2B SaaS companies see revenue concentration in Q4 (enterprise budget cycles) and Q1 (new fiscal year commitments). A company calculating runway in November on strong Q4 collections may find net burn materially higher in Q1 and Q2. Model revenue seasonality into the forward runway projection — a company with 16 months of runway in November may functionally have 11 months if Q1-Q2 is typically 30% lighter on cash receipts.

4. Ignoring committed future expenses not yet in the cost base

A signed lease for new office space, a committed contractor engagement, or an agency retainer that starts next month are committed outflows that will increase gross burn. These are not in the current month's expense run rate but are in the future burn trajectory. A rigorous runway calculation identifies committed expenses in the next 3-6 months and incorporates them into the forward projection.

5. Confusing revenue growth with cash timing

A company closing a large annual contract improves ARR and, in the collection month, improves net burn significantly. But if the contract is invoiced net-30 or net-60, the cash may not arrive for 1-2 months after the deal closes. Runway calculated on the deal-close date — before cash arrives — will be understated. Conversely, a company that just collected 6 months of upfront annual contracts will see an artificially low net burn this month that will not repeat for 6 months. Cash timing and revenue recognition are different; runway calculations require cash timing.

How Fairview tracks runway automatically

Fairview's Forecast Confidence Engine calculates runway monthly using actual cash balances from connected bank accounts and cash-basis net burn from Stripe, QuickBooks, and Xero integrations. The calculation uses a 3-month rolling average for net burn rather than a single-month snapshot, reducing the distortion from one-time payments or large annual contract collections. Runway is displayed on the Operating Dashboard alongside net burn trend and burn multiple.

When runway drops below 14 months — the threshold that triggers the Series B fundraise preparation window — Fairview's Next-Best Action Engine surfaces a specific, time-bound alert: "Runway at current net burn: 13.8 months. Series B fundraise typically takes 4-6 months from first pitch to cash. Recommend initiating fundraise process within 30 days." The alert quantifies the current position, contextualizes it against typical fundraise timelines, and provides a specific recommended action date — not a generic warning.

→ See how the Forecast Confidence Engine works

Runway vs cash runway

Both terms describe months of operation before zero, but they differ in whether they account for burn evolution. Cash runway is static. Runway (in a rigorous model) is dynamic. Use cash runway for conservative stress-testing; use dynamic runway for planning.

Frequently asked questions

Sources

1. a16z: How to Think About Burn Rate and Runway
2. Y Combinator: Default Alive or Default Dead (Paul Graham)
3. Bessemer Venture Partners State of the Cloud 2025