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What is the difference between burn rate and runway?
Burn rate is how fast you SPEND money (cash out, $/month). Runway is how long you SURVIVE on current cash (months until $0). Burn × runway = total cash. A startup with $500k cash and $50k/mo burn has 10 months of runway. Net burn (spending − revenue) is the more useful number than gross burn.
The full answer
The two metrics defined
Both metrics describe the relationship between cash spent + cash available. They're sides of the same coin.
- Burn rate — monthly cash outflow. Gross burn = total monthly expenses. Net burn = expenses minus revenue.
- Runway — months until cash hits $0. Formula: Current cash / Monthly net burn.
Example: $1M in the bank, spending $80k/mo, earning $30k/mo. Net burn = $50k/mo. Runway = 20 months.
Side-by-side comparison
| Property | Burn rate | Runway |
|---|---|---|
| Unit | $/month (e.g., $50,000/mo) | Months (e.g., 18 months) |
| What it measures | Spending velocity | Time until insolvency |
| Direction | Higher is WORSE | Higher is BETTER |
| Formula | Gross: total spend / month. Net: (spend − revenue) / month | Cash / Net burn |
| Trends | Should DECREASE if maturing | Should STAY ≥12 months for safety |
| Reaction lever | Cut spending, raise revenue | Raise money, cut burn, OR grow revenue |
| Time-frame | This-month / quarter | Forward-looking, planning horizon |
| Investor question | "What's your burn?" | "How much runway do you have?" |
| Common trap | Reporting gross when net is what matters | Calculating with revenue that hasn't materialized |
Gross burn vs net burn
- Gross burn = total monthly outflow. Salaries + rent + cloud + tools + everything.
- Net burn = gross burn − monthly revenue.
A company spending $100k/mo and earning $40k/mo has $60k net burn. Net burn is the operationally relevant number — that's what depletes cash. Gross burn is the worst-case if revenue dries up.
When founders say "I'm burning $60k/mo" they usually mean net burn. When investors ask, they often want both.
Why net burn is more useful
Two companies with identical $100k/mo expenses: - Company A: $0 revenue. Net burn = $100k/mo. With $1M cash: 10 months runway. - Company B: $80k/mo revenue. Net burn = $20k/mo. With $1M cash: 50 months runway.
Same gross burn; 5× difference in runway. Net burn captures business reality.
Runway thresholds (calibrated against venture norms)
| Runway | Verdict | Action |
|---|---|---|
| <6 months | Critical | Raise money NOW (assume 3-6 months to close) or aggressive cost cuts |
| 6-12 months | Watch carefully | Optimize burn; start raising 9 months before $0 |
| 12-18 months | Healthy | Default startup runway; raise when ready, not from desperation |
| 18-24 months | Strong | Ample buffer; can survive bad market |
| 24+ months | Excellent | Capital-efficient growth or over-capitalized |
The 18-month benchmark (David Sacks, Brad Feld, others) is canonical: gives 12 months to operate + 6 months to raise.
Burn multiple — the modern unit-economics metric
Burn multiple = Net Burn / Net New ARR added in same period. Lower = more capital-efficient growth.
| Burn multiple | Verdict |
|---|---|
| <1× | Best-in-class (rare; usually only at scale) |
| 1-2× | Healthy growth (gold-standard early/mid stage) |
| 2-3× | Acceptable (typical for high-growth Series A-B) |
| >3× | Inefficient growth; burning more than producing |
If you burn $1M to add $500k Net New ARR, burn multiple = 2×. That's reasonable. If you burn $1M to add $200k ARR, burn multiple = 5×. Investigate before next raise.
Common burn/runway mistakes
- Optimistic revenue projections — calculating runway using expected revenue that hasn't materialized; use trailing-3-month average revenue
- Excluding one-time costs — runway based on "normalized" burn excluding "one-time" items that keep appearing as new "one-time" items
- Ignoring funding-round closure timing — assuming you close a round on day 1 of approaching $0; realistic is 3-6 months
- Not tracking by-segment burn — engineering burn vs sales burn vs marketing burn; cutting one is different from cutting another
- Currency exposure — multi-currency operations + FX rate swings affect runway materially
The classic "default alive vs default dead" framing
Paul Graham 2015 essay: a startup is "default alive" if current revenue growth would make it profitable before cash runs out, otherwise "default dead." Most startups are default dead and don't realize it. Quick check:
- If you stopped raising tomorrow + your current revenue growth continued + your costs stayed flat — would you reach profitability before $0?
- Yes = default alive
- No = default dead (need to raise OR cut costs OR accelerate revenue)
The exercise forces honest evaluation of whether your business model works without external capital.
Cross-reference: see /pages/what-is/customer-acquisition-cost + /pages/what-is/monthly-recurring-revenue + /pages/what-is-the-difference-between/cac-and-ltv.
Time ranges by condition
| Condition | Duration | Note |
|---|---|---|
| Critical runway (<6 months) | Raise immediately or cut aggressively | — |
| Default healthy runway | 12-18 months (canonical startup benchmark) | — |
| Strong runway | 18-24 months | — |
| Time to raise a round | 3-6 months from start to wire | — |
| Healthy burn multiple | <2× (Net Burn / Net New ARR) | — |
What changes the time
- Gross vs Net burn. Gross excludes revenue. Net = Gross − Revenue. Net is operationally relevant; Gross is worst-case planning
- Revenue assumption stability. Trailing-3-month revenue average more reliable than forward-looking. Optimistic revenue assumptions destroy runway calculations
- Cost variability. "One-time" costs that keep appearing are actually recurring; runway calculations using normalized burn often understate true burn by 10-30%
- Funding-round timing. Assume 3-6 months to close a round. Start raising at 9-12 months runway, not at 3 months desperation-level
Common questions
What's a "good" burn rate?
There's no universal number — it's relative to your funding and runway. $50k/mo burn is great if you have $5M in the bank (8+ years runway) and disastrous if you have $200k (4 months). The question is always "burn relative to runway." Healthy: burn that gives 12-18 months runway WITH realistic growth assumptions. Investors evaluate burn multiple (Net Burn / Net New ARR) more than absolute burn — efficiency matters more than spending level.
When should I start raising my next round?
When you have 9-12 months of runway, not when you have 3. Reasons: (1) Fundraising typically takes 3-6 months from first meeting to wire. (2) Raising from a position of strength (still 6 months runway when closing) yields better terms than raising from desperation. (3) Market conditions can shift quickly — having buffer time means you can wait for favorable conditions instead of accepting any terms. The phrase "raise when you don't need to" is canonical for this reason.
How do I reduce burn without hurting growth?
Three highest-leverage moves: (1) Audit cloud + SaaS tool spend — most companies overspend by 20-40% on tools. Quarterly audit recovers significant burn. (2) Slow hiring — extending time-to-hire by 30 days conserves cash without reducing existing capacity. (3) Renegotiate vendor contracts at renewal — 10-20% discounts common when threatening to leave. AVOID: cutting marketing (kills growth flywheel); cutting engineering (kills product velocity); freezing customer support (kills retention).
What's "default alive vs default dead"?
Paul Graham's framing: would your startup reach profitability before $0 if you stopped raising NEW capital and your current revenue growth continued? Yes = "default alive" (you control your destiny). No = "default dead" (you depend on raising another round to survive). Most early-stage startups are default dead and don't realize it. The exercise forces honest evaluation: does your business model actually work at scale, or does it only work with infinite cheap capital?
Sources
We cite primary research, expert practice, and authoritative reference. Higher-tier sources weighted heavier. See methodology.
- T2Paul Graham, "Default Alive or Default Dead?" — Canonical essay on startup burn-vs-runway thinking
- T2Brad Feld, "Burn Rate Discipline" — Founder-investor framework for burn/runway management across stages
- T1Bessemer Venture Partners "Burn Multiple" — Burn multiple as the modern capital-efficiency metric; benchmarks by stage
- T2David Sacks, "How to Manage Your Burn" — Origin of the Burn Multiple framework; comparison to traditional cash-burn metrics
- T2YC Startup School curriculum — Standard runway calculation methodology + raise-timing guidance for early-stage founders
Cite this page
de Vries, P. (2026). What is the difference between burn rate and runway?. AskedWell. Retrieved 2026-05-26, from https://askedwell.com/pages/what-is-the-difference-between/burn-and-runway
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