Burn Rate and Runway: The Two Numbers That Decide Everything

Why these two numbers sit above all the others

Most startups do not fail because the product was wrong. They fail because they ran out of money before they found out.

Burn rate and runway are the two numbers that describe that risk directly, and they are the two an experienced investor will ask about within the first ten minutes.

Gross burn vs net burn

Gross burn is all the cash leaving the business in a month. Salaries, rent, hosting, tools, marketing, professional fees - everything.

Net burn is gross burn minus the cash coming in.

Net burn = Cash out − Cash in

Example. In July a company pays out ₹24,00,000 and collects ₹9,00,000 from customers.

• Gross burn: ₹24,00,000
• Net burn: ₹15,00,000

Both matter, and they tell you different things. Net burn is what depletes the bank account, so it drives runway. Gross burn tells you what your cost base actually is - which matters because if revenue dips, gross burn is what you are left carrying.

A company with ₹24 lakh gross burn and ₹15 lakh net burn is in a materially different position from one with ₹16 lakh gross burn and ₹15 lakh net burn, even though their runway is nearly identical. The first has revenue that could grow. The second has almost none.

Use cash, not accrued expenses. An invoice you have received and not paid is not burn yet.

Runway

Runway (months) = Cash in bank / Net burn per month

₹2,70,00,000 in the bank against ₹15,00,000 net burn is eighteen months of runway.

Two refinements that make the number honest:

Use an average, not last month. A single month with an annual insurance payment or a big marketing push is not representative. Three-month trailing average is usually about right.

Model burn going up if it is going to. If you are hiring four people next quarter, your runway is not what today's burn implies. Build a simple month-by-month forecast rather than dividing one number by another. The forecast is almost always shorter than the division suggests, and the gap is where founders get surprised.

What good looks like

Runway remaining	Practical position
24+ months	Comfortable. Build.
18–24 months	Healthy post-raise position.
12–18 months	Start preparing the raise. Get materials and metrics in order.
9–12 months	Actively fundraising.
6–9 months	Fundraising urgently, and it shows in the terms.
< 6 months	Bridge, cut, or both. Your leverage is largely gone.

The reason the "start at 9–12 months" advice is so consistent is arithmetic. A round takes three to six months from first conversation to funds received, and that assumes it goes well. Starting at six months of runway means you are signing whatever is on the table at month two of the process.

Investors know this. A founder with three months of cash is negotiating against a visible deadline, and the terms reflect it.

Reducing burn without breaking the company

If runway is short, the order in which you cut matters more than the total.

Look at these first:

• Software subscriptions nobody uses. Audit every tool against actual logins.
• Paid acquisition with a payback period longer than your runway. If a customer takes fourteen months to repay their acquisition cost and you have nine months of cash, that spend is not an investment.
• Contractors and agencies on retainers rather than deliverables.
• Office space you are not using at the size you are paying for.

Be careful with these:

• Engineering headcount. It is usually the largest line and cutting it is the fastest way to reduce burn, which is exactly why it is tempting. It is also how you stop shipping and remove the reason anyone would fund you.
• Anything that touches existing customers. Churn is far more expensive than the cost you saved.

Consider these:

• Founder salary reduction. Meaningful, and signals commitment to investors.
• Renegotiating payment terms. Collecting faster and paying slower improves cash without cutting anything.
• Annual prepayment discounts from customers. Cash now at a discount is often worth it when runway is the binding constraint.

Extending runway from the revenue side

Cutting costs is one lever. It is not the only one, and founders reach for it first because it is entirely within their control.

Collect faster. Receivables sitting at ninety days are cash you have earned and cannot spend. Tightening collections is often the single fastest improvement available, and it costs nothing.

Invoice earlier. Milestone or upfront billing rather than on completion.

Sell annual contracts. A twelve-month prepayment converts a year of future revenue into cash today.

The number nobody calculates and everybody should

Months to default-alive. At your current growth rate and cost base, do you reach profitability before you run out of cash?

Project revenue growth and burn forward month by month. If the lines cross before the cash runs out, you are default-alive: you could survive without raising, which puts you in the strongest possible negotiating position. If they do not cross, you are default-dead, and raising is not optional.

Paul Graham's point about this was that most founders do not know which one they are, and that the answer changes how you should behave. Founders who are default-alive can be selective about investors. Founders who are default-dead and think they are default-alive tend to discover the difference late.

What to report to your board and investors

Every month, four numbers and one sentence:

1. Cash in bank at month end
2. Net burn for the month
3. Runway in months, based on a forward forecast rather than a simple division
4. Revenue for the month
5. One sentence on anything that materially changed

That is it. Investors who receive this consistently are far easier to go back to for a bridge than investors who hear from you when there is a problem.

The one-line summary

Net burn depletes the bank; gross burn is the cost base you carry if revenue moves. Runway is your remaining decision-making freedom, and it starts shrinking as leverage well before it hits zero - which is why the right time to raise is when you do not yet need to.