Burn Rate Calculator: Gross Burn, Net Burn & Runway for Startups

29% of startups die because they run out of cash. Do not let yours be one of them.

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In 30 seconds: Visualize your runway under different spending and growth scenarios. You will know exactly when you need to raise or cut. Deterministic calculation with auditable formulas. The result is indicative — adjust the assumptions to reflect your real operation.

Runway isn't measured by simply dividing cash by burn — it also depends on how burn changes over months (hiring, churn, enterprise deals). Paul Graham coined the 'default alive' rule: a startup is default alive if, assuming current revenue and burn growth, it reaches profitability before cash runs out. If not, it is default dead and depends on closing another round. This calculator gives the honest first projection — for A/B/C scenarios use the advanced simulator.

Methodology

Variable Expenses = Revenue × (% Variable ÷ 100)

Monthly Net Flow = Revenue − Fixed Expenses − Variable Expenses

Accounts Receivable = Revenue × (Collection Days ÷ 30)

Balance[month 1] = Reserve + Net Flow − Accounts Receivable

Balance[month N] = Balance[month N-1] + Net Flow

Runway = Reserve ÷ (Fixed Expenses + Variable Expenses)

Variables

Revenue
Average monthly revenue of the business.
Fixed Expenses
Expenses that don't vary with sales (rent, payroll).
% Variable
Percentage of revenue spent on variable expenses.
Collection Days
Average number of days it takes customers to pay.
Reserve
Cash available at the start of the projection.

Practical example

Seed startup with $1.5M USD in the bank, monthly burn $200,000 (gross), current MRR $80,000 growing 8% month over month.

Net burn month 1: $200,000 − $80,000 = $120,000.

If MRR grows steadily 8% monthly: month 6 MRR = $80,000 × 1.08^5 = $117,548. Net burn month 6: $200,000 − $117,548 = $82,452.

Linear runway at current burn: $1,500,000 ÷ $120,000 = 12.5 months. Real runway with growing MRR: ~17 months (cash depletes more slowly as revenue grows).

If hiring runs away and fixed costs go to $260,000 with MRR unchanged: runway drops to 10 months. Each extra $20K of burn costs 2 months of runway in this profile.

Operating recommendation: if net burn does not project to hit $0 before month 18 (standard runway to close Series A), pause non-essential hiring and shift budget to revenue initiatives. Series A success rate with runway < 9 months drops below 30% per First Round Capital — investors smell the urgency and push for harsher terms.

Interpretation

A positive monthly net flow doesn't guarantee liquidity. If your customers pay late, you can have cash problems even though you're profitable.

Runway tells you how many months your company survives without revenue. Less than 3 months is a risk zone; at least 6 is recommended.

If the projection line dips below zero, your business will need external financing at that point.

Review this projection monthly against actuals. The gap between projected and actual measures your cash management.

Assumptions and limitations

  • Assumes constant monthly revenue and expenses (no seasonality).
  • Accounts receivable impact only the first month of the projection.
  • Does not consider credit lines, financing or capital injections.
  • Does not include taxes, depreciation or financial expenses.
  • Runway assumes a complete revenue stop; in practice it would be partial.

When to use this calculator

  • When starting a new business. Before signing leases or hiring staff, project your cash flow to know how many months you can operate before revenue covers expenses. Many profitable businesses fail due to early-months illiquidity.

  • When your customers pay on credit. If you sell at 30, 60 or 90 days, invoicing doesn't reflect cash on hand. Cash flow shows when you actually receive the money and whether you can meet obligations while waiting.

  • To decide whether you can take on a major expense. Before buying equipment, hiring an employee or investing in inventory, simulate how it affects your cash balance over the next 6-12 months.

  • When negotiating payment terms with suppliers. If your flow is positive but tight in certain months, you can negotiate paying at 60 days instead of 30 to smooth expense peaks.

  • To determine how much working capital you need. Cash flow shows the lowest point of your balance — that's the minimum reserve you need to operate without surprises.

  • When a bank or investor asks for financial projections. The cash flow statement is one of the three basic financial statements they evaluate to grant credit or investment.

Common mistakes

  • Confusing profit with cash. You can have positive accounting profit and still run out of cash. If you sold $100,000 but your customers haven't paid yet, you don't have $100,000 in the bank. Cash flow measures real money, not payment promises.

  • Not accounting for seasonality. Most businesses have strong and weak months. A restaurant in a tourist area may bill twice as much in December as in September. Projecting constant revenue creates a false sense of security.

  • Underestimating average collection days. Customers rarely pay on agreed terms. If the contract says 30 days, the real average is usually 45-60 days. Use real collection data to project.

  • Forgetting irregular expenses. Year-end bonuses, annual insurance, license renewals, equipment maintenance and annual tax payments are expenses that don't appear every month but can empty your cash when they arrive.

  • Not maintaining an emergency reserve. The minimum rule is 3 months of fixed expenses in reserve. For businesses with corporate customers paying on credit, the recommendation rises to 6 months. Without reserves, any collection delay or unexpected expense creates a crisis.

  • Projecting growth without considering the cost of growth. If sales rise 50%, you probably need more inventory, more staff and more space. Growth consumes cash before generating it.

Industry use cases

Pre-seed

Burn $20-60K/month, runway target 18-24 months. Zero revenue is normal. Reserves determine validation speed. Each $8K/month hire costs 4-6 weeks of runway in this profile — hire only if the problem they solve is validated.

Seed

Burn $80-200K/month with growing MRR. Runway target 12-18 months post-round. Watch for hires that raise burn 30%+ per month — a senior hire goes from exception to default without you noticing. Keep hiring under a revenue cap: every $30K of new MRR justifies one hire.

Series A

Burn $250-600K/month. Key metric: net burn (gross burn − MRR). Default alive: net burn negative within 6 months. If burn multiple > 2x for 3 sustained quarters, the model is burning capital without returns — cut before the board does.

Series B+

High burn ($1M+/month) paired with growing ARR. Measure efficiency with Burn Multiple = Net Burn ÷ Net New ARR. < 1.0 is excellent, 1.0-2.0 healthy, > 2.0 problematic. Bessemer's cohort reports a 1.4 average Burn Multiple for SaaS Series B in 2024.

Methodology and assumptions

How results are calculated, what we assume when modeling, and where the method loses precision.

Formula

Ending balance = Opening balance + Inflows − Outflows · Runway = Balance ÷ |Monthly burn|

Assumptions

  • Inflows and outflows distributed evenly through the month.
  • Lines of credit or factoring not included unless entered as additional inflows.
  • Inflation treated as flat within the projection horizon.

Applicability limits

  • Runway becomes unreliable with less than 3 months of history.
  • Large one-off events (annual taxes, year-end bonuses) must be entered as point items.
  • Does not model depreciation: it works on cash, not accounting profit.

Sources

  • Brealey, Myers & Allen — Principles of Corporate Finance (13th ed., McGraw-Hill).
  • Internal editorial estimate based on industry best practices.

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Complete guide

What burn rate is

Burn rate is the speed at which a startup burns its capital, measured in dollars per month. It is the most critical metric of seed and Series A stages because it defines runway — the months the company survives without raising more capital. If runway runs out, nothing else matters: not product-market fit, not MRR growth, not the team.

Gross burn rate vs net burn rate

  • Gross burn rate. Total monthly operating spend: payroll, cloud, marketing, SaaS tools, office. Ignores revenue.
  • Net burn rate. Gross burn minus MRR (monthly revenue). It is the real drop in the bank account.

A startup with 250,000 USD of gross burn and 120,000 of MRR has a net burn of 130,000. On the expense sheet it looks identical to one with no billing, but in real runway it lasts twice as long.

Runway formula

Runway (months) = Available cash ÷ Monthly net burn rate

Numeric example. Seed startup with 1.8 million USD in the bank, gross burn of 210,000, MRR of 55,000. Net burn = 155,000. Runway = 1,800,000 ÷ 155,000 = 11.6 months. Standard fund rule from Bessemer and Craft Ventures: start the next fundraise when runway falls below 9 months. This founder has ~2.5 months before going out to pitch.

Burn multiple: David Sacks's metric

Popularized by David Sacks (Craft Ventures), burn multiple measures how much you burn for every dollar of new ARR.

Burn multiple = Net burn ÷ Net new ARR

References: under 1x is exceptional; 1x-2x is good; 2x-3x is suspect; above 3x indicates you are buying revenue with capital. Median Series A startups in 2025 operate at 1.6x (Carta, Battery Ventures).

Burn rate benchmarks by stage (2025)

StageMedian gross burnPost-round runway
Pre-seed25-40k USD/month18-24 months
Seed75-100k USD/month18-24 months
Series A350-500k USD/month18-24 months
Series B800k-1.5M USD/month24-30 months

Data from Carta and SVB 2025. Heads up: the gap between rounds has stretched to ~696 days and only ~15 out of every 100 seed startups raise a Series A. That is why many founders now target 24-30 months of runway, not 18.

When to go out and raise the next round

Practical rule: go to market with 9-12 months of runway. In 2025 a fundraise takes 4-7 months from first meeting to wire. Going out with 6 months is negotiating from weakness; going out with 3 is a distressed bridge round.

How to calculate your burn rate with real data

  1. Open the last three full bank statements. Do not use the P&L: P&L lies with revenue recognition timing; bank statements do not.
  2. Compute the balance drop month over month. If the balance went from 2.4M to 2.21M to 2.02M, the average net burn is ~190k/month.
  3. For gross burn, add the average MRR for the period to net burn.
  4. Divide current balance by the average net burn: that is your real runway in months.

QuickBooks, Mercury Treasury, Brex Cash Flow and Pilot compute these numbers automatically if you connect bank and accounting system. The hard part is not arithmetic: it is being honest about what counts as recurring MRR and what is one-time revenue.

How to reduce burn without killing growth

  1. Freeze hiring in non-revenue functions (ops, BD, generalists) before engineering and direct sales. The first cut attacks spend that does not generate ARR.
  2. Renegotiate AWS/GCP commits — 25%-40% of seed startups overbuy in their first year per Scale Venture Partners benchmarks.
  3. Kill ad channels with CAC payback longer than 18 months. If a channel does not pay back in less time than the contract cycle, it is not growth, it is an incinerator.
  4. Venture debt or revenue-based financing when ARR exceeds 1M USD. Capchase, Pipe and Brex extend runway 6-12 months without cap-table dilution.
  5. Raise prices for new customers. It improves the burn multiple without touching the cost base and without cutting velocity: legacy customers stay on old pricing, new ones absorb the increase.

The goal is not minimum burn: it is maximum capital efficiency. Cutting 50% of burn and 70% of growth worsens the burn multiple. 2025 Series A investors read the ratio, not the absolute number, and penalize clumsy cuts as much as waste.

Mistakes that kill startups before the next round

  • Confusing cash with runway. 1M USD in the bank with burn growing 15% monthly is not 10 months of runway: it is ~7.
  • Over-hiring post-round. The most common Series A error: doubling headcount in four months without proportional revenue. Burn multiple spikes to 3x+ and the next round prices flat or down.
  • Ignoring the revenue conversion cycle. With annual-prepay contracts cash lands up front but ARR grows smoothly; with monthly, cash is slow but ARR looks fast. Burn multiple changes with contract, not just with product.
  • No financing plan B. Assuming the next round closes on time. In 2024-2025 startups with product and traction die because the gap between rounds stretched past 22 months and they had no SAFE bridge or venture debt ready.

Magic Number and capital efficiency in 2025-2026

Beyond burn multiple, investors in 2025-2026 are applying two additional capital-efficiency metrics that a rigorous burn rate model must address:

Magic Number = Net new ARR × 4 / Sales & Marketing spend in the prior quarter. A value above 0.75 indicates efficient go-to-market; below 0.5 signals you are buying revenue too expensively for the burn you are accepting. The Magic Number normalizes GTM efficiency across revenue scales — a $2M ARR startup spending $500K/quarter on S&M generating $200K net new ARR records 0.40 — acquisition efficiency well below the threshold for a confident Series A. Bessemer Venture Partners coined this metric; it appears in the Series A screen of most US tier-one funds.

ARR per FTE = Annual Recurring Revenue / Total headcount. A capital-efficient SaaS startup targets $150K-$250K ARR/FTE at seed, $200K-$350K entering Series A, $350K+ at Series B. Startups burning $300K/month with 12 FTEs and $600K ARR are at $50K ARR/FTE — a ratio that flags over-staffing relative to monetized output, regardless of what the pipeline spreadsheet says.

Bridge rounds and SAFE mechanics

When runway falls below the fundraising threshold and a full priced round is not achievable in time, founders have three instruments:

  1. SAFE bridge (YC Post-Money SAFE). The simplest: existing investors write a new check at a valuation cap slightly above the last priced round. No new board seat, minimal legal cost ($8-15K vs $80-150K for a priced round). Closes in 2-4 weeks vs 4-6 months for a priced round. Risk: SAFEs accumulate and dilute heavily at the next priced round if the cap is not carefully negotiated.
  1. Venture debt. Non-dilutive capital (Silicon Valley Bank historically, now Western Technology Investment, Hercules, Trinity Capital). Typically 20-30% of last equity round, 12-36 month term, 9-12% interest. Extends runway 4-8 months with zero equity dilution. Requires revenue traction ($500K+ ARR minimum for most providers) and financial covenants. Do not confuse with revenue-based financing (Capchase, Pipe, Arc): RBF is cheaper (6-9%) but caps at 4-6 months of MRR.
  1. Pay-to-extend. Reducing burn to minimum viable operation (critical engineering only, pause all G&A and marketing) while closing the next round. The cash saved by cutting $80K/month of payroll gives 2-3 additional months, which can be the difference between a round that closes and one that doesn't.

Layoff math: staff cost vs runway extension

The hardest burn-rate decision is the RIF (reduction in force). The math: a 15-person layoff at a $200K average fully-loaded cost per head reduces gross burn by $250K/month (12.5 heads effective after 2-week notice and severance, plus one-time severance cost of ~$50K). If current net burn is $400K and the layoff reduces it to $150K on a $2M cash balance, runway extends from 5 months to 13.3 months — a materially different fundraising position. But the model must also account for: (1) revenue impact if any of the laid-off employees managed key accounts or critical engineering deliverables; (2) recruiter and re-hiring cost if growth resumes in 12 months; (3) morale impact on the remaining team, which historically increases voluntary turnover 15-25% in the 3-6 months after a layoff. The simulator lets you model headcount by department and project the net burn and runway impact of any combination of cuts before the decision is made.

Red flags that predict cash crisis before it hits

  • AR over 60 days rising. Accounts receivable aging above 60 days with enterprise customers means cash is slower than the revenue line implies. Net burn should always be computed on cash-in, not on invoices sent.
  • Payroll timing mismatch. Bi-weekly payroll on the 1st and 15th can create a low-balance week that triggers bank covenants even when the quarterly burn is technically healthy.
  • Undisclosed AP. AP to contractors, SaaS vendors and legal not shown in the cash burn model understates real net burn by 10-20% at seed stage startups that invoice-pay quarterly.
  • Seasonal revenue with flat payroll. An enterprise SaaS startup with Q4-weighted renewals and a flat $350K/month payroll will show a 4-month apparent runway going into Q2 even though the Q4 renewals will reset it. Model seasonality explicitly.

Illustrative case

Composite case for instructional purposes: combines sector dynamics with realistic figures. Names are fictional and do not represent a specific company.

Pelcyr Labs is a seed-stage B2B SaaS startup building AI compliance monitoring for fintechs. Founded in 2023 in Austin by two ex-Plaid engineers, it closed its seed round of 3.5M USD in Q2 2025 on a post-money SAFE of 15M USD with a mid-tier VC and two strategic angels. Nine months into the seed, CEO Priya Raman opened the cap-table dashboard and saw numbers that did not line up with a clean Series A narrative.

Cash balance: 1,980,000 USD. Average gross burn over the last three months: 280,000 USD/month. Revenue (ARR of 852K USD, MRR 71K USD vs 42K USD nine months earlier). Net burn: 223K USD/month. Runway: 8.9 months. Burn multiple computed on quarterly net new ARR (348K USD annualized from the last three months): 1.92x.

Under Sacks's framework, 1.92x is inside the "good" band, but 2025 Series A investors are anchoring lead term sheets at burn multiples near 1.5x for seed-to-A transitions. Priya's technical co-founder ran three scenarios in the simulator. Status quo produced a 8.9-month runway and a flat burn multiple — a round raised from weakness. Aggressive cut (freeze 2 AE hires, renegotiate AWS commit, pause G&A hiring, kill LinkedIn ads) dropped gross burn to 228K USD, net burn to 171K USD, extended runway to 11.6 months and improved burn multiple to 1.47x. A layer of revenue-based financing on top (500K USD at 9% from Capchase) extended the envelope to 14.2 months with no equity dilution.

Priya took the middle path: cut hiring, keep R&D at full speed, renegotiate AWS, and raise a 750K USD SAFE bridge with existing seed investors at a slight step-up. Three months later she opened Series A conversations with 13 months of runway, a 1.5x burn multiple and MRR of 104K USD growing 18% MoM. Three tier-one funds issued term sheets within six weeks. Series A closed at 42M USD post-money, 2.8x the previous round, with a lead that cited burn efficiency as the single line item that moved the operation from "watch" to "term sheet".

From theory to calculation

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Sector reference ranges

Indicative ranges based on public sector literature and operational observation. Your business may differ — use the numbers as a starting point, not as a target.

MetricValueSource
Startups citing 'running out of cash' as cause of failure38% (root cause); 70% (symptom)CB Insights, Top Reasons Startups Fail 2024
Median gross burn — seed-stage SaaS (2025)80,000 USD/monthCarta State of Private Markets H2 2024
Median gross burn — Series A SaaS (2025)350,000 USD/monthCarta State of Private Markets H2 2024
Median burn multiple — Series A SaaS (2025)1.6xBattery Ventures Software Benchmarks 2025
Gap between seed round and Series A (2024)~696 daysCarta, Seed-to-A Conversion 2024
Seed startups that successfully raise Series A~15%Scaleup Finance / Carta 2025
S&M share of total burn — seed to Series A23% → 35% of total burnScale Venture Partners, SaaS Benchmarks 2025
Recommended post-round runway (2025)24-30 monthsSVB State of the Markets H1 2025

Frequently asked questions

1What is a startup's burn rate?
Burn rate is the speed at which a startup spends cash each month. Gross burn = total monthly operating spend. Net burn = gross burn minus monthly revenue, i.e., the real monthly drop in bank balance.
2How is a startup's runway calculated?
Runway (in months) = current cash balance ÷ monthly net burn. Example: 1.8M USD in the bank with net burn of 150K USD/month = 12 months of runway before raising capital or growing revenue becomes mandatory.
3What is a healthy burn rate for an early-stage startup?
Median seed SaaS burn is 75K-100K USD/month and Series A is 350K-500K USD/month (Carta, 2025). What matters more than the absolute number is capital efficiency — measured by burn multiple. Target: under 2.0x at seed and under 1.5x entering Series A.
4How many months of runway should a startup have?
18-24 months post-round is the historical benchmark. In 2025, with the gap between seed and Series A stretching to ~696 days, many founders target 24-30 months. Start the next fundraise when runway falls below 9-12 months so you do not negotiate from weakness.
5What is the difference between gross burn and net burn?
Gross burn counts all monthly operating spend regardless of revenue. Net burn subtracts monthly revenue to show the real cash drop. A company with 250K USD gross burn and 100K USD MRR has a net burn of 150K USD — real runway is computed on net, not gross.
6When should I start raising the next round?
Start your fundraise with 9-12 months of runway. In 2025 a round takes 4-7 months from first meeting to wire. Going out with 6 months is negotiating from weakness; going out with 3 usually forces a distressed bridge or a down round.
7How do I reduce my burn rate without slowing growth?
Freeze hires in non-revenue functions, renegotiate cloud commits (25%-40% of early-stage startups over-commit), kill paid channels with CAC payback over 18 months, extend vendor terms, and consider venture debt or revenue-based financing when ARR exceeds 1M USD. Raising prices for new customers is the fastest lever on burn multiple.
8What is burn multiple and how is it calculated?
Burn multiple = net burn ÷ net new ARR over the same period. Coined by David Sacks (Craft Ventures). Under 1x is exceptional, 1-2x is good, 2-3x is suspect, above 3x is bad. Median SaaS Series A in 2025 is ~1.6x (Carta, Battery Ventures).

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Last updated: April 30, 2026 · Reviewed by the Simúlalo editorial team. Figures and benchmarks are indicative; verify with your own data before deciding.

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