Flintroom Get the app

Runway calculator

Most of them divide cash by burn and hand you a number. This one grows your spend, grows your revenue, gives you the month you actually run out, and then tells you what gets asked about it.

Your numbers

What you can actually spend, net of anything already owed.
Everything going out: payroll, contractors, tools, rent.
Everything coming in. Leave it empty if you are pre-revenue.
Empty assumes your costs never move. Few companies manage that.
Empty is the honest floor. Anything above it is a claim you will be asked to back.

Cash runs out

—

Add your cash balance

What gets asked about this number

The figure is not the end of the exercise. It is the thing somebody is about to question. These four are asked of every runway number ever quoted. Fill the calculator in and the ones drawn from your own figures join them, marked.

  1. Is that cash figure gross, or net of what you already owe?

    Bank balance and available cash are different numbers. Payables, deferred payroll and a tax bill tend to land in the same quarter as everything else, and the gap between the two figures is where a stated runway quietly shortens.

  2. Does the spend include the hires you have already made offers to?

    An accepted offer is committed spend that has not reached a bank statement yet. It is the most common reason a runway figure moves a month after it was first quoted.

  3. What is this number if the round takes a quarter longer than planned?

    Processes slip. The answer separates a plan from a hope, and whoever is asking has watched a great many timelines move to the right.

  4. Which single line item, if it doubled, moves this date the most?

    Concentration risk in one sentence. If one vendor, one hire or one infrastructure bill can move the date on its own, it lands better when you name it before anyone else does.

How this is calculated, and where the usual version goes wrong

The standard runway calculation is cash divided by net burn. It is correct arithmetic and a poor forecast, because it holds two things still that are never still: what you spend and what you earn. A company spending 3% more each month reaches zero months earlier than the division says, and the gap widens the further out you look.

Gross burn and net burn are different numbers

Gross burn is everything leaving the account. Net burn is gross burn minus revenue: the amount the bank balance actually falls by. Runway is always calculated on net burn, and quoting the two interchangeably is the most common way a founder and an investor end up describing different companies. This page asks for spend and revenue separately so the distinction is made for you.

Default alive or default dead

Paul Graham's framing, and the reason the two growth fields exist. A company is default alive if, on its current trajectory and with no new money, it reaches profitability before it reaches zero. Being default dead is not a failure: most companies are, and that is what a round is for. It changes what the round is: a choice about speed, or a requirement for survival. Whoever is on the other side of the table knows which one they are looking at.

What this does not model

Nothing seasonal, no step changes, no financing. Spend and revenue each compound at one steady rate, which is a simplification and an honest one, because the alternative is asking for a twelve-month plan, and a page that asks for a plan is a spreadsheet with extra steps. If your costs move in jumps when you hire, run it twice: once at today's spend, once at what it becomes the month the offers land.

How much runway is enough

The convention since 2022 has been eighteen to twenty-four months, and it is a convention rather than a rule. What sits underneath it is that a round takes three to six months to close, and you want to be raising from a position where you could walk away. Under twelve months, that leverage is thinning. Under six, the conversation has already changed.

Terms on this page

Gross burn
Everything leaving the bank in a month, before any revenue is counted.
Net burn
Gross burn minus revenue. The amount the balance actually falls by, and the one runway is calculated on.
Runway
How long the cash lasts at the current net burn. Quoted in months, acted on as a date.
Default alive
Reaching profitability on the current trajectory, with no new funding, before the money runs out.
Burn multiple
Net burn divided by net new annual recurring revenue. A measure of how much you spend to add a unit of growth. Not computed here, and the follow-up question if you are a SaaS business.

A number is only as good as your answer about it.

Flintroom is a rehearsal room. A panel of AI interrogators presses on your argument out loud, quotes your own deck back at you, and does not accept the first answer. Then a coach rebuilds the ones that came loose.

Get it on Google Play

Other free tools