MRR and startup runway calculator (2026)

Cash ÷ burn is fine at zero revenue. The moment you have MRR growing at any rate, it's wrong in both directions and you can't tell which.

If you're growing 15% a month, the naive formula badly under-reports your runway — you might have 18 real months and think you have 9, and cut a hire you needed. If you're flat or churning, it over-reports, and you find out three months before zero instead of nine.

Simulating month by month costs nothing and gets both cases right. It also surfaces the number that matters more than runway: the month net burn crosses zero. If that month arrives before your cash does, you don't need to raise at all.

Cash is money in the bank you can actually spend. Not invoiced, not committed, not a credit line you haven't drawn. Subtract tax you owe but haven't paid — that is the single most common way founders overstate runway, and it fails at the worst possible moment.

MRR is recurring revenue only. A one-off consulting invoice is not MRR. Annual contracts count at one twelfth. If you're mixing the two, model them separately or you'll plan around revenue that isn't coming back next month.

Burn is everything leaving the account monthly, including the founder salaries you're not taking yet but will. A model built on unpaid founders quietly breaks the month you start paying yourselves.

Growth rate should be your trailing three-month average, not last month's. One good month is noise. Three is a trend, and even then, sustained 15%+ monthly growth is rare — if your model needs it, the model is the problem.

Under 6 months. You are in the raise-or-cut zone. Both take longer than planned — a raise is typically 3–6 months from first conversation to money in the bank, and cuts take a month to actually show in the numbers. Starting either at 4 months is starting late.

6 to 12 months. Enough to run one real experiment and see it resolve. Pick the single riskiest assumption in the business and spend this window resolving it, rather than spreading across three.

12 to 18 months. Comfortable. The risk shifts from running out of money to running out of urgency, which is less visible and roughly as fatal.

Beyond 18 months. Either you're profitable, in which case ignore this, or you raised a lot and the question is whether you're spending fast enough to justify what you raised.

The break-even month in the output is worth more attention than the runway number. Every month of runway is borrowed. Break-even is the month the borrowing stops.

Two levers move it, and they're not equal. Cutting burn moves it immediately and predictably — the effect lands next month, and it caps your ceiling. Growing MRR moves it later but compounds, and doesn't cap anything. Under six months of runway, cut, because you need a certain effect fast. With twelve or more, grow, because you can afford to wait for the compounding.

The founders who get this wrong grow when they should cut, because growing feels like progress and cutting feels like failure. It isn't — a cut that buys you six more months to find the thing that works is the opposite of failure. It's the decision that keeps the option open.

One number to keep next to the other two: months to your next irreversible commitment. A twelve-month lease signed at nine months of runway is a decision made on your behalf by your past self, and it doesn't appear anywhere in a cash model until it's already binding.