Your spreadsheet says you have 14.2 months of runway. That number feels solid. It isn't.
Cash doesn't behave like a physics problem. Revenue timing slips. Costs surprise you. The hire you planned for Q2 happens in Q3. A big client pays late. Your "14.2 months" could be 9 months or 18, depending on which of these things happen and when.
What matters is the probability you reach the milestone before cash runs out.
Why single-number forecasts mislead
Spreadsheet runway models are deterministic. One cash balance, one burn rate, one growth assumption. Divide and you get a number. The model is internally consistent, which is exactly what makes it persuasive and dangerous.
The problem isn't that your spreadsheet is wrong. It's that it shows you one scenario when you're actually facing thousands. Decisions about raise timing, investor commitments, and hiring plans need to account for the range, not just the midpoint.
Decisions about raise timing, hiring plans, and milestone commitments need to account for the shape of that distribution, not just its midpoint.
What this calculator does differently
The Cash Runway Calculator runs Monte Carlo simulations: 1,000 scenarios with realistic variances in revenue timing, cost fluctuations, and payment delays. Instead of one number, you get a probability distribution.
P10 (worst realistic case): Only 10% of simulations were worse than this.
P50 (median): Half of simulations fell above, half below.
P90 (best realistic case): Only 10% of simulations were better.
So instead of "14.2 months runway," you might see: "P10 is 9 months, P50 is 13 months, P90 is 17 months." That range is where your actual decisions live.
Beyond runway: what else it shows you
The probability distribution is the foundation, but three outputs make it operationally useful.
**Milestone feasibility.** Pick a target date and goal: product launch, revenue milestone, next funding round. The calculator shows the probability you reach it before cash runs out. If the odds are 40%, you know before committing.
**Funding gap.** How much cash you need to reach your milestone with 80% confidence, accounting for variance rather than guessing or padding by feel.
**Decision deadline.** The latest you can start fundraising without negotiating from weakness, given your runway volatility and a realistic raise timeline.
Who this is for
This is built for finance leads and founders who've constructed a runway spreadsheet and don't fully trust it, or who are planning a raise and need to reverse-engineer timing.
If you have a milestone (product launch, hiring plan, revenue target) and want to know whether cash actually supports it, this gives you the answer in 5-10 minutes rather than building scenarios manually. If you're six months from a raise and need to know when the window closes, you'll see it.
It's also useful if you're not raising at all. Knowing your real runway range changes how you commit to plans, regardless of whether exit, independence, or simply better forecasting is the goal.
How It works
You input your current cash, monthly burn, revenue trajectory, and target milestones. The calculator runs 1,000 simulations and returns your probability distribution, milestone feasibility, and decision timeline.
Takes 5–10 minutes. Full results after email, no paid tier for the core analysis.
See the range
Your runway isn't 14.2 months. It's a probability distribution shaped by every variable your spreadsheet treats as fixed.
Better to plan around probabilities than false precision.