Startup Runway Simulator: When Does $200K in the Bank Actually Run Out?
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$200,000 cash, $25,000/month burn, $5,000 MRR growing 12%/month — the revenue ramp reaches breakeven before the static "cash ÷ burn" runway estimate would suggest you're out of money. Model your own burn and growth rate.
Why “cash ÷ burn” isn’t the real runway number
We ran a common early-stage scenario through the calculator: $200,000 in the bank, $25,000/month burn, starting at $5,000 in monthly revenue growing 12% month over month. A naive “cash ÷ burn” estimate would say 8 months of runway — but that ignores revenue entirely. Once you model the ramp, this scenario reaches breakeven (revenue covering burn) well before the cash would actually run out, which is a materially different, and more useful, answer than the static estimate.
How the math works
Each month: net burn = monthly burn rate − that month’s revenue. Cash balance carries forward month to month. Revenue compounds at your assumed monthly growth rate. The tool reports two different milestones: the month cash would hit zero (if the ramp isn’t fast enough), and the month revenue first covers burn (breakeven) — these can happen in either order, and knowing which one comes first is the whole point of running this instead of a flat cash-divided-by-burn estimate.
What this tool doesn’t model: burn rate stepping up as you hire (the single biggest real-world deviation from this flat-line assumption), lumpy revenue (annual contracts, seasonal businesses), a funding round changing the cash balance mid-projection, or the psychological/practical lag between “the model says we’re in trouble” and actually cutting costs or closing a raise.
Math runs locally. Inputs never leave your browser. Source on github.
Where this simulation is too optimistic
- Burn rate almost never stays flat. The moment you hire, burn jumps in a step, not a smooth line. If a hire is planned partway through your horizon, run two separate projections — one for the pre-hire burn, one for the post-hire burn — rather than trusting a single flat-rate number for the whole period.
- Revenue growth compounding smoothly is the exception, not the rule. Real early-stage revenue is lumpy — a big annual contract lands in one month, churn takes a bite the next. Treat the growth-rate input as your realistic trailing average, and stress-test with a meaningfully lower rate to see how much margin for error you actually have.
- You need lead time to raise or cut, not a same-month reaction. If the model shows cash running out in month 10, that’s not when you start raising — fundraising typically takes 3-6 months from first conversation to close. Treat the runway number as your deadline to have already started that process, not the date to react.
- “Breakeven” here means revenue covers burn, not that you’re actually profitable after taxes and reserves. Once you’re regularly hitting this threshold, budget for the real accounting picture (taxes, contingency reserves) before declaring the company self-sustaining.
What to actually do with this number
- Use your trailing 3-6 month actual revenue growth rate, not an aspirational target, as the input.
- Re-run the model with a step-up in burn for any planned hire, rather than trusting a single flat number across the whole horizon.
- If cash runs out before breakeven, start the fundraising or cost-cutting conversation 3-6 months before that projected date, not when the balance actually gets low.
- Re-run monthly with actual figures — the value of this tool is in catching the trend early, not in a single one-time projection.
- Treat “breakeven” as a milestone to celebrate carefully, not a signal to stop tracking cash closely.