Startup Runway Calculator: Formula, Examples, and a Founder's Guide (2026)

What is startup runway?

Startup runway is the number of months your business can keep operating before it runs out of cash, assuming nothing else changes. It is the single most important number to know as a founder, because it tells you how much time you have to either reach profitability or close your next round of funding.

A runway calculator turns three inputs (cash on hand, monthly revenue, and monthly expenses) into one output (months of runway). The maths is simple. The discipline is in keeping the inputs honest.

The runway formula

The basic startup runway formula is:

runway (months) = cash on hand / net monthly burn

Where net monthly burn is your monthly cash outflow minus your monthly cash inflow:

net burn = monthly expenses - monthly revenue

If your revenue exceeds your expenses, you are not burning cash, so runway is effectively infinite. Most early-stage startups have a positive net burn, which means they are spending more than they are earning each month.

A worked example

Let's say you are a pre-seed founder with the following:

• Cash in the bank: $400,000
• Monthly expenses: $55,000 (salaries, rent, infra, tools)
• Monthly revenue: $5,000 (early paying customers)

Net monthly burn = $55,000 - $5,000 = $50,000.

Runway = $400,000 / $50,000 = 8 months.

That means you have eight months to either grow revenue, cut burn, or close a round before the bank account hits zero. Most founders aim to start a fundraise with at least six months of runway in reserve, so in this example you would already be very close to the point where you should be talking to investors.

Gross burn vs net burn

A common runway calculator mistake is to confuse gross burn with net burn.

• Gross burn is your total monthly cash outflow, ignoring any revenue you bring in.
• Net burn is gross burn minus revenue. This is the number you use for runway.

For more on the distinction, read our burn rate calculator guide.

What is a healthy runway by stage?

There is no universal answer, but these are the rough benchmarks investors expect to see at each stage:

Below 6 months of runway, most investors will treat your raise as a bridge or a rescue rather than a clean round. Plan accordingly.

Common mistakes when calculating runway

1. Using a single static burn number. Your burn is not flat. Hires, infrastructure, marketing, and contractor costs change month by month. A static number will mislead you by 20% or more after a few months.
2. Ignoring lumpy expenses. Annual SaaS bills, quarterly tax payments, deposits on office space. They all compress runway in the months they hit.
3. Treating optimistic revenue projections as cash on hand. Pipeline is not cash. Until the money clears, do not include it in your runway calculation.
4. Forgetting the fundraise lead time. A round takes three to six months from kickoff to wire. If you start when you have four months of cash left, you are already late.

How to extend your runway without raising

The fastest way to add months to your runway is to cut burn, not grow revenue. A 10% burn cut today often adds more runway than a 10% revenue bump that takes six months to land.

• Audit subscription tools quarterly. Most teams pay for 30% they don't use.
• Right-size cloud infrastructure. Reserved instances, dropping unused environments, and switching to cheaper regions can cut bills by 20 to 40%.
• Renegotiate annual contracts. Vendors will discount 10 to 20% to keep a paying customer.
• Pause hiring above the must-fill bar. One unfilled senior role is often a month of runway.

A free runway calculator built for founders

RocketRunway is a runway calculator and scenario modeller built for founders modelling cash for the first time. Plug in your line items (salaries, infrastructure, revenue, growth assumptions), and we generate a runway projection you can iterate on. Compare two to four scenarios side by side, plot fundraising milestones on the chart, and share a read-only link with your co-founders or investors in a click.

The 7-day Pro trial gives you full access. No credit card required at signup.