Burn Rate and Runway: How Long Can Your Startup Survive?

What are burn rate and runway?

Burn rate measures how quickly your company consumes cash. Runway estimates how long available cash will last under stated assumptions. They help you decide what you can afford and when you must change the plan.

For cash planning, use actual operating cash movements and keep financing flows separate:

Measure	Calculation	Meaning
Gross burn	Monthly operating cash outflows	The cash cost of running the business
Net burn	Operating outflows minus operating inflows	Cash consumed by operations
Static runway	Usable cash ÷ positive monthly net burn	Months remaining if that burn stays constant

Carta provides a gross-versus-net burn framework. Revenue and cash collections can occur at different times, so reconcile your planning model to bank movements rather than assuming they are interchangeable.

Why it matters

A company can show growing revenue while running short of cash. Annual collections, delayed invoices, hiring, taxes, and one-time payments all change the timing.

Runway is useful when it produces decisions: which milestone to fund, when to hire, when to begin financing conversations, and what action to take if sales arrive late. Company runway is separate from the founder's personal household runway.

Worked example: a changing spending plan

All figures are invented for teaching, not targets or forecasts. Assume unrestricted business cash of $300,000, monthly operating payments of $45,000, and monthly customer collections of $15,000.

• Gross burn: $45,000 per month.
• Net burn: $45,000 − $15,000 = $30,000 per month.
• Static runway: $300,000 ÷ $30,000 = 10 months.

Now assume spending and collections change:

Period	Monthly outflows	Monthly inflows	Monthly net burn	Cash after period
Start	—	—	—	$300,000
Months 1–3	$45,000	$15,000	$30,000	$210,000
Months 4–6	$55,000	$20,000	$35,000	$105,000
Months 7–9	$55,000	$25,000	$30,000	$15,000

If month-ten burn remains $30,000, the remaining cash covers about half a month. The projected runway is roughly 9.5 months, not the original static ten. Actual payment dates can make the cash shortage arrive sooner.

If collections stay at $15,000 after month three while spending rises to $55,000, the remaining $210,000 lasts 5.25 additional months, for roughly 8.25 months total.

Build a cash forecast you can act on

1. Start with usable cash. Identify restricted balances, obligations, and any minimum reserve you intend to preserve.
2. List payments by date. Include payroll, taxes, vendors, debt service, capital purchases, and one-time costs.
3. Forecast collections. Separate signed customer commitments, pipeline, and assumptions. Include collection delays.
4. Show financing separately. A planned investment is not available cash until it closes and funds arrive.
5. Calculate ending cash. Opening cash + all inflows − all outflows = ending cash.
6. Compare actuals with the forecast. Explain differences and update the next periods.

Use monthly planning for the broader horizon and a weekly view when timing is tight. Simple runway division is a rough screen; a dated forecast is more useful for deciding whether you can pay obligations.

Choose a milestone and a decision date

Suppose the next useful proof is a set of renewing customers. Estimate the work, cost, and time required to get there, plus room for delays. Set a date for reviewing progress before cash forces the decision.

Possible actions include reducing discretionary spending, delaying a hire, collecting receivables, changing pricing, or seeking financing. Model the implementation cost and delay of each action. Annual prepayments can improve cash timing while creating future delivery obligations.

Default alive describes a business whose current trajectory can reach profitability before cash runs out without another raise. It is a scenario-dependent claim. Cash-flow break-even and accounting profitability can arrive at different times.

What investors are looking for

Prepare to explain:

• What is gross and net burn, and how were they measured?
• What milestone does current cash buy?
• Which hires or costs are essential to reaching it?
• What changes if collections are late or revenue grows more slowly?
• When will you take corrective action?

Show a forecast with sources, dated assumptions, and downside cases. There is no universal burn rate or runway that suits every stage and business model. A larger budget needs a credible explanation of what it will accomplish.

Common mistakes

• Dividing cash by gross burn when customer collections materially offset spending.
• Using accounting revenue as if it were cash received.
• Counting an unsigned funding round as available money.
• Ignoring hiring plans, annual bills, taxes, or debt payments.
• Calling zero or negative net burn “infinite runway” without checking future obligations.
• Waiting until the final month of cash to change the plan.

Founder checklist

Reconcile the starting balance, define your burn method, and list all major cash obligations. Build base and downside forecasts. Assign a milestone, a minimum cash threshold, and an owner for each possible action.

Your next action: update the cash forecast with the latest bank movements and identify the earliest date when the plan needs a decision.

Sources and further reading

• Carta: Burn Rate Calculator and Formula
• SparkLaunch: Startup Costs for Founders

References checked November 10, 2026. Worked examples are simplified teaching scenarios, not financial forecasts.