Startup Runway Calculator
How long does the money last? Enter cash, monthly expenses, and monthly revenue for your net burn, runway, and zero-cash date. Add revenue and expense growth rates and it simulates the trajectory month by month — telling you whether you're default alive (break-even before the cash runs out) or default dead, and when to start fundraising. All in your browser.
Month-by-month projection
| Mo | Revenue | Expenses | Net burn | Ending cash |
|---|
"Runway" is how long your cash lasts at the current net burn. The classic framing: a startup is default alive if its growth would reach profitability before the money runs out, and default dead if not. Add monthly growth rates for revenue and expenses and the calculator simulates the trajectory month by month instead of assuming everything stays flat.
Runway is a trajectory, not a balance
The bank balance tells you where you are; runway tells you where you're headed. At a steady net burn, your cash is a countdown — and the only things that move the date are spending less or earning more. Watching runway (not just the balance) is what turns "we have money" into "we have nine months, so the next raise or the path to profitability has to land before then."
The default-alive question
The sharpest way to read your runway is to ask whether you're default alive: if nothing changes except your existing growth, do you reach profitability before the cash runs out? If yes, you're in control and can choose to raise on your terms. If no, you have a deadline — and the time to act on it is now, not when the runway is measured in weeks. Fundraising and turnarounds both take longer than anyone plans for.
This calculator answers the question directly: set your revenue growth rate (and expense growth, if headcount is climbing) and it compounds both forward month by month. You get a verdict — default alive with the break-even month and the cash buffer at that point, or default dead with the zero-cash date and a fundraise-by date nine months ahead of it. The month-by-month projection table shows the whole path, so you can see exactly which months are the squeeze.
Related
- Break-even calculator — units to cover fixed costs
- Marketing tools hub — ROAS, CPC/CPM, margin, and more
- Personal finance hub — all our money calculators
- ROI calculator — return on an investment
FAQ
Is anything I enter sent to a server?
No. The calculator runs entirely in your browser — open DevTools → Network and confirm. Your financials never leave the tab.
How is runway calculated?
Runway (in months) = cash ÷ net monthly burn, where net burn is monthly expenses minus monthly revenue. If you have $200,000 and burn a net $22,000/month, that's about 9 months. If revenue meets or exceeds expenses, net burn is zero or negative and runway is effectively infinite — you're cash-flow positive.
What's the difference between gross and net burn?
Gross burn is your total monthly spend. Net burn is gross burn minus revenue — the rate your bank balance actually drops. Runway is driven by net burn, because revenue offsets some of the spend. This calculator asks for expenses and revenue separately and computes the net for you.
What does 'default alive' vs 'default dead' mean?
A framing popularized by Paul Graham: a startup is default alive if, on its current growth and spending, it would become profitable before the money runs out — and default dead if it wouldn't. It's a sharper question than 'how much runway do we have,' because it forces you to look at the trajectory, not just the balance. Knowing which you are changes every decision.
How much runway should I keep?
A common rule of thumb is to raise or reach profitability with 6+ months of buffer, and many founders aim to keep 12–18 months of runway after a raise. Fundraising takes longer than you expect, so hitting a dangerously low runway before starting is a classic, avoidable mistake. Watch the zero-cash date and act well before it.
How do the growth rates change the calculation?
With growth rates set, the calculator stops assuming a flat burn and simulates month by month (up to 120 months): revenue compounds at your revenue growth rate, expenses at the expense growth rate, and cash falls by each month's net burn. Two outcomes are possible: revenue overtakes expenses while cash is still positive — default alive, shown with the break-even month and the cash you'd have left — or cash hits zero first, giving your simulated runway and zero-cash date. Example: $200k cash, $30k expenses, $8k revenue growing 10%/month breaks even in month 14 with about $26k to spare.
Why does a few percent of monthly growth matter so much?
Because it compounds. 10%/month is 3.1× a year — $8k of MRR becomes $25k in 12 months. That's the entire difference between the flat model (9 months of runway, default dead) and the growth model (break-even before the cash runs out, default alive) on identical starting numbers. It cuts the other way too: expense growth compounds against you, which is why the simulator takes both rates.
When should I start fundraising?
Work back from the zero-cash date. A seed-to-A raise typically takes 3–6 months of active work — plus preparation, and a buffer for the term-sheet-to-wire gap — so the calculator flags a start date 9 months before your projected zero. If that date is already behind you, the honest reading is: start now, and cut burn in parallel so the raise isn't happening from a position of weakness.