How to Calculate Your Startup Runway (With Free Calculator)

Every founder needs to know one number: how long until you run out of money. This is your runway. Get it wrong and you are making decisions in the dark.

What Is Runway?

Runway is the time you have before cash hits zero. If you have $100,000 in the bank and burn $10,000 per month, your runway is 10 months.

Simple math. Critical insight.

The Basic Formula

Runway = Current Cash / Monthly Burn Rate

Your burn rate is everything you spend minus any revenue coming in. For pre-revenue startups, this is just your costs. For those with revenue, subtract it from expenses to get net burn.

Why Most Founders Get This Wrong

They forget the ramp. Your burn rate today is not your burn rate in six months. If you are hiring, marketing, or building inventory, costs go up.

Smart founders model three scenarios:

• Conservative: Burn stays flat
• Realistic: Burn grows 10-20% monthly
• Aggressive: Rapid hiring and marketing spend

Each scenario tells a different story about when you need to raise, hit revenue, or cut costs.

The Metrics That Matter

Beyond raw runway, track these:

Cash Zero Date: The actual calendar date you hit zero. Put it in your calendar. Stare at it weekly.

Months to Breakeven: If you have a revenue plan, when does it cover costs?

Funding Buffer: Never plan to hit zero. Most founders want 3-6 months of buffer before starting a raise.

When to Start Raising

Rule of thumb: start fundraising when you have 6-9 months of runway left. Raises take longer than you think. Deals fall through. Markets shift.

If you wait until you have 3 months left, you are negotiating from weakness. Desperation shows. Terms get worse.

Making It Real

Spreadsheets work but they are static. Your business changes weekly. You need a living model you can adjust as reality hits.

I built a free runway calculator that lets you plug in your numbers and see exactly where you stand. Add your cash, revenue, expenses, and growth assumptions. See your runway in months and your cash zero date on a calendar.

Try the free startup runway calculator here

No signup required. Just the math you need to make smart decisions.

The Bottom Line

Runway is not accounting. It is survival. Know your number. Update it weekly. Make decisions before the market makes them for you.

The founders who survive are not the ones with the most funding. They are the ones who saw the cliff coming and turned early.