Burn rate & runway calculator: how many months until cash runs out
Calculate monthly burn rate, cash runway in months, zero-cash date, and default alive month. Growth-adjusted modeling for realistic projections. Free, no signup, shareable result.
Inputs
Results
How to read this calculation
Gross Burn = Monthly Operating Expenses
Net Burn = Monthly Operating Expenses − Monthly Revenue
Runway (static) = Cash Balance ÷ Net Burn (in months)
Default Alive = Month when Revenue ≥ Expenses (at growth rate)
With growth: simulate month-by-month, applying growth rate to revenue
until cash hits zero OR revenue covers expenses.
Runway is how many months until cash runs out at current burn. It's the single most important number for any pre-profitable business. Operators who don't know their runway precisely make worse decisions about hiring, spending, and fundraising timing. Calculate it monthly, not quarterly.
Default alive (Paul Graham's term) is when revenue grows to cover expenses without additional capital. A startup at $80K revenue, $125K expenses, and 10% monthly growth becomes default alive in month 5 (when revenue compounds past $125K). If you're default alive within your runway, you don't need to raise. If you're not, you do — start the process at least 6 months before zero date.
The fastest way to extend runway is to cut, not raise. A 20% cut to monthly expenses on a $125K burn extends runway by 25-30% immediately. The same effect requires raising 25-30% more capital — which takes 4-6 months. Most pre-profitable operators wait too long to cut. By the time runway is critical, the cuts that would have extended runway by months can only extend it by weeks.
Frequently asked questions
The questions founders and operators most commonly ask about burn rate and runway.
What's the difference between gross burn and net burn?
Gross burn is total monthly cash outflow regardless of revenue — the full expense base. Net burn is gross burn minus monthly revenue. A startup with $150K expenses and $80K revenue has $150K gross burn and $70K net burn. Investors typically focus on net burn (what's actually consuming cash) but gross burn matters too as a measure of operational scale and cost discipline.
What is 'default alive' and why does it matter?
Default alive (Paul Graham's term) is when current revenue at current growth rate eventually exceeds expenses before cash runs out — meaning the business can survive without additional funding. Default dead means the opposite. Default alive companies have optionality (raise or don't). Default dead companies must raise. This is the most useful single framing for whether a fundraise is mandatory.
How much runway should I have before starting a fundraise?
9-12 months minimum, ideally 12-18 months. Fundraises take 4-6 months from outreach to wire transfer — longer for first-time founders or harder markets. Starting at 6 months runway means closing with 0-2 months left, which is desperate and shows in valuation terms. Starting at 12-18 months runway means closing with 6-12 months left, which is fundraising from strength.
How do I extend runway quickly?
Cut first, raise second. A 20% cut to monthly expenses extends runway by 25-30% immediately; raising 20% more capital takes 4-6 months and dilutes the cap table. Most operators wait too long to cut. Common high-impact cuts: pause non-essential hiring, reduce ad spend to validated channels only, renegotiate vendor contracts, defer founder compensation, sublease excess office space.
Find the burn you can cut without losing growth
The audit reviews your tooling, headcount, vendor contracts, and operational spend to identify cuts that extend runway without slowing the business. Free, no signup, no sales call required.
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