Definition
Runway is a financial planning metric that estimates how long a company can continue operating with the cash it currently has available, assuming its future cash inflows and outflows follow a specified pattern.
It is particularly important for startups that are not yet cash-flow positive and depend on existing cash reserves or external financing to fund operations.
A common simplified calculation is:
Runway = Available Cash ÷ Monthly Net Burn
For example, a company with $1.2 million in available cash and a monthly net burn of $100,000 has approximately 12 months of runway, assuming the burn rate remains constant and there are no other material cash movements.
Runway is an estimate, not a guaranteed operating period. Changes in revenue, spending, hiring, fundraising, or other cash movements can materially change it.
How is runway calculated?
The simplest calculation uses available cash and average monthly net burn:
Runway = Available Cash ÷ Average Monthly Net Burn
For example:
Available cash: $2 million
Average monthly net burn: $200,000
$2 million ÷ $200,000 = 10 months
The company therefore has approximately 10 months of runway under those assumptions.
For companies with highly variable cash flows, using an average burn over several months can provide a more useful estimate than using a single month's burn.
What is available cash?
Available cash generally refers to cash that the company can actually use to fund operations.
It may include:
Cash held in bank accounts
Cash equivalents, depending on the company's definition
Other immediately accessible funds
It should not automatically include committed but undrawn financing, expected future investment, or revenue that has not yet been collected.
The exact definition should be consistent with the company's financial planning methodology.
Runway and burn rate
Runway is directly related to burn rate.
Burn rate measures how quickly a company is consuming cash.
Runway estimates how long its existing cash can support that level of consumption.
For example:
Metric | Amount |
|---|---|
Available cash | $3 million |
Monthly net burn | $250,000 |
Estimated runway | 12 months |
If monthly net burn increases to $300,000, the same $3 million would provide only:
$3 million ÷ $300,000 = 10 months
This demonstrates why runway can change even when the company's cash balance has not changed.
→ Burn Rate
Gross burn vs. net burn for runway
Runway is usually calculated using net burn when the objective is to estimate how quickly the company's cash balance is declining.
For example:
Monthly cash outflows: $500,000
Monthly cash inflows: $200,000
Net burn: $300,000
If available cash is $3 million:
$3 million ÷ $300,000 = 10 months
Using gross burn instead would produce:
$3 million ÷ $500,000 = 6 months
That may not accurately represent the company's actual cash consumption if the $200,000 inflow is recurring and reliably collectible.
The appropriate calculation depends on the company's financial situation and planning assumptions.
What can shorten runway?
Runway can decrease when:
Hiring increases
Salaries increase
Marketing spending rises
Product development costs increase
Expansion requires additional capital
Revenue declines
Customers pay more slowly
Unexpected expenses arise
Debt repayments increase
A company can therefore lose runway even if its headline cash balance initially appears healthy.
What can extend runway?
Runway can increase through:
Raising additional capital
Increasing revenue
Improving collection of receivables
Reducing operating expenses
Slowing hiring
Improving gross margins
Reducing customer acquisition costs
Delaying expansion
Restructuring other cash commitments
Different methods have different implications for growth.
Reducing expenditure may extend runway but could also slow product development or revenue growth. Increasing revenue may extend runway while simultaneously strengthening the business.
Why does runway matter to founders?
Runway helps founders determine when financial decisions need to be made.
It can inform decisions about:
Hiring
Spending
Expansion
Fundraising
Cost reduction
Product investment
Cash management
A company with 18 months of runway has a different set of options from a company with three months of runway.
The metric therefore helps founders make decisions before a cash shortage becomes urgent.
Runway and fundraising
Runway is particularly important when planning a financing round.
A startup needs to consider:
Current cash → Current burn → Expected future burn → Milestones remaining → Fundraising timeline
Fundraising can take longer than expected, particularly when investor diligence, negotiations, and legal documentation are involved.
For that reason, founders often need to begin fundraising before the company reaches the end of its runway.
The appropriate timing depends on the company's growth, financing environment, investor interest, and ability to reach meaningful milestones before raising additional capital.
Runway is not a fixed countdown
A common mistake is to treat runway as an exact expiration date.
If a company has 12 months of runway today, it does not necessarily mean that it will run out of cash exactly 12 months from now.
The calculation assumes particular cash-flow conditions.
For example, if revenue grows faster than expected, runway may increase. If the company hires more employees or experiences weaker sales, runway may decrease.
A more useful approach is to model several scenarios.
Base case
Expected revenue and spending.
Upside case
Higher revenue or lower-than-expected expenditure.
Downside case
Lower revenue or higher-than-expected expenditure.
Scenario planning provides a more realistic view of financial resilience than relying on one runway number.
Runway vs. cash balance
Cash balance tells you how much cash the company has.
Runway tells you how long that cash may last under defined assumptions.
For example:
Company A:
Cash: $2 million
Monthly net burn: $100,000
Runway: 20 months
Company B:
Cash: $2 million
Monthly net burn: $400,000
Runway: 5 months
Both companies have the same cash balance but very different financial positions.
Example
A startup has $1.5 million in available cash.
Its average monthly cash outflows are $250,000 and average monthly cash inflows are $100,000.
Its approximate monthly net burn is:
$250,000 − $100,000 = $150,000
Its estimated runway is:
$1.5 million ÷ $150,000 = 10 months
The founders therefore have approximately 10 months of runway under the current assumptions.
If they plan to raise another financing round, they need to account for the time required to prepare, approach investors, complete due diligence, negotiate terms, and close the transaction.
Common misconception
Having 12 months of runway means the company has 12 months before it needs to fundraise.
Not necessarily.
A company may need to begin fundraising well before its calculated runway ends because fundraising itself takes time and because future investors may want the company to demonstrate specific milestones before investing.
Runway is therefore a planning metric, not a fundraising deadline.
