How-to guide

How to use the Runway & Burn Calculator

The most important number you're not tracking closely enough: how long your money lasts. Here's how to use it, with three examples.

Runway is the number that decides everything else — hiring, spending, when to raise. This tells you how many months of cash you have left, in plain English.

What this tool does

You enter your cash on hand and your monthly cash in and out; it shows your net monthly burn and how many months of runway you have.

Who it's for

Founders and operators who want a clear, honest read on how long the business can keep running.

How to use it — step by step

  1. Enter cash on hand. What's actually in the bank today.
  2. Enter monthly cash in and out. Real cash, not accounting profit.
  3. Read your runway. Net burn and months remaining.
  4. Decide with it. Use the number to time hires, cuts, or a raise.

How to read your result

If runway is under ~6 months, you're in raise-or-cut territory now, not later. Runway shrinks faster than people expect once burn creeps up — recheck it monthly.

Worked examples

The same tool behaves differently depending on what you put in. Here are 3 situations.

Flat burn

Inputs: $300k cash, $50k in, $90k out.

What the tool shows: Net burn $40k/month → 7.5 months of runway.

What to do: Start a raise now — fundraising takes longer than 7 months.

Burn creeping up

Inputs: Same cash, but spend rising each month.

What the tool shows: Shows runway is shorter than a flat calc suggests once burn grows.

What to do: Freeze new spend until you've re-based the number.

Revenue offsetting burn

Inputs: Growing revenue reduces net burn.

What the tool shows: Longer runway as cash-in rises — but only if revenue is real cash, not invoices.

What to do: Confirm collections before you count the runway.

Common questions

Cash or profit? Cash — runway is about the bank balance, not accounting profit.

How often should I check? Monthly, and before any big spending decision.

What's a safe runway? Enough to close a raise with margin — usually 12+ months when you start.

A helpful estimate, not a guarantee. This tool works only off the numbers and assumptions you enter — it can't see your whole picture. Use it to get oriented and pressure-test your thinking, then sanity-check the big calls with an advisor. It isn't financial, tax, or legal advice.