SaaS Burn Rate: How to Calculate Gross and Net Burn Correctly

Burn rate is the speed at which your company consumes cash. Misunderstanding it leads to miscalculating runway, overestimating survival time, and raising at the wrong moment. This guide covers the precise definitions, how to calculate both gross and net burn, why trailing 3-month burn matters, benchmarks by stage, and how to break burn by department to see where your company is most efficient.

Gross Burn: Total Cash Out per Month

Gross burn is every pound/euro that leaves your bank account each month, regardless of revenue coming in. It includes payroll, vendor costs, rent, insurance, software subscriptions, contractor payments, tax payments, and any other cash outflow.

Formula:

Gross Burn = Total Monthly Cash Out

Includes:
  Payroll (salaries + benefits + payroll tax)
  Contractors
  Cloud infrastructure (AWS, Google Cloud)
  Third-party APIs and integrations
  Office rent
  Insurance
  Software subscriptions and tools
  Vendor invoices
  Travel and meals
  Legal and accounting
  Equipment and capex

Example Company (Month 5):

• Payroll: €85,000
• Contractors: €12,000
• AWS and infrastructure: €18,000
• Office rent: €8,000
• Insurance: €3,500
• Software tools: €4,200
• Other opex (legal, accounting, travel): €9,300
• Gross Burn: €140,000

Gross burn tells you your minimum cost of running the business. If you collected zero revenue, you'd burn €140,000 monthly. This metric is useful for understanding your cost structure and negotiating with vendors. If your gross burn is rising month-over-month (due to headcount additions or opex increases), you're moving toward a more expensive company, which extends your burn timeline unless revenue grows commensurately.

Net Burn: Gross Burn Minus Revenue Collected

Net burn is the actual cash loss each month. It's the metric that determines your runway. If gross burn is €140,000 and you collect €95,000 in customer payments, your net burn is €45,000. This is the amount your cash balance declines each month.

Formula:

Net Burn = Gross Burn - Cash Revenue Collected

Example:
  Gross Burn: €140,000
  Cash Collected: €95,000
  Net Burn: €45,000

Why Revenue Collected, Not Revenue Recognised?

The critical distinction: revenue recognised (P&L, accrual accounting) versus revenue collected (cash). A customer signing a €12,000 annual contract on April 1 has you recognise €1,000 revenue in April. But if the customer pays net-30, you don't collect the €12,000 cash until May 1 (or later if payment fails).

For burn rate calculation, use only cash collected. If you're waiting on customer invoices to pay, that cash isn't in your bank account yet; it shouldn't reduce your net burn calculation. Using revenue recognised instead of collected understates burn and miscalculates runway.

Trailing 3-Month Burn: The Right Methodology

Don't use a single month's burn to calculate runway. Monthly burn is volatile. One month might have a customer renewal payment in (reducing burn), the next month no renewal (increasing burn). Annual insurance renewal in Q4 creates a burn spike. Bonus payouts in December inflate December burn.

The Correct Approach:

Calculate average net burn over the trailing 3 months. This smooths out one-time events and gives a more reliable picture of sustainable burn rate.

Example:

• Month 1 net burn: €48,000
• Month 2 net burn: €52,000
• Month 3 net burn: €45,000 (lower because of customer renewal payment)
• Average (trailing 3-month): €48,333

If you have €430,000 cash on hand, your runway is €430,000 / €48,333 = 8.9 months. This is more realistic than using Month 3's €45,000 burn (which would give 9.5 months runway) or Month 1's €48,000 (which would give 8.9 months).

Update this calculation monthly. Each new month, drop the oldest month from the calculation and add the newest. This rolling 3-month average adapts to changing business dynamics without whipsawing on a single bad or good month.

Monthly vs Weekly Burn Tracking

Monthly is the standard for investor presentations and runway calculations. Some companies track weekly burn for real-time dashboards, but weekly data is too noisy to be actionable. Stick with monthly for decision-making. Weekly is useful only if you're in a burn-reduction crisis (RIF, emergency cost-cutting); in normal operations, monthly is sufficient.

Burn by Department: Identifying Efficiency

Break your company into cost centres and calculate burn for each. This reveals where your cash is flowing and which departments create the most value per euro burned.

Typical Series A SaaS Company (€1m ARR, €500k MRR):

How to Use This Data:

If your Engineering burn is 44% and delivering strong product improvements (high NRR, low churn), that department is efficient. Protect it when cutting costs. If Sales burn is 19% and acquiring customers at reasonable CAC (under 12 months payback), that's efficient too.

But if Marketing burn is 16% and generating low-efficiency customers (CAC payback 24+ months, low LTV), that's a candidate for cuts. Reallocate that €80k to more efficient channels (organic, referral, product-led growth).

Burn Rate Benchmarks by ARR Stage

Context: These numbers vary dramatically by vertical and geography. A European B2B SaaS company has lower salary costs than US Bay Area equivalents. A capital-intensive AI company burns faster than a lightweight SaaS startup. Use these benchmarks as directional guidance, not as targets.

How Billing Terms Affect Net Burn

A company with 50% annual billing and 50% monthly billing has very different monthly net burn than a 100% monthly billing company, even with identical revenue.

Example (both companies have €100k MRR / €1.2m ARR):

Scenario A: 100% Monthly Billing

• Monthly collections: €100,000 (consistent, every month)
• Gross burn: €135,000
• Net burn: €35,000
• Runway (€2.5m cash): 71.4 months

Scenario B: 50% Annual, 50% Monthly

• Month 1: Collections €650k (half of annual customers pay upfront) + €50k (monthly) = €700k
• Month 2-12: Collections €50k (monthly) + deferred revenue converted to revenue = ~€100k (once amortised)
• Gross burn: €135,000
• Month 1 net burn: -€565,000 (inflow!)
• Months 2-12 net burn: €35,000

In Scenario B, Month 1 shows huge cash inflow, which looks amazing. But by Month 2, net burn reverts to €35,000 (same as Scenario A). The difference: Scenario B frontloads cash, giving the company a cushion. This is why annual billing is powerful for early-stage SaaS.

Implication for Runway: If your company has a mix of annual and monthly billing, your month-to-month burn varies. Use trailing 3-month average to get a smooth number. Don't rely on Month 1 burn (which might have an annual renewal) to predict Month 12 survival.

Payment Failures and Write-Offs

Not all revenue collected is cash. Some customers' credit card payments fail (chargeback, insufficient funds). On average, plan for 1-3% of monthly invoiced revenue to fail to collect. This reduces net burn improvement.

If you invoice €100,000 and expect 2% failure rate, actual cash collected is €98,000. Your net burn is higher by €2,000 than projected.

Key Takeaways

• Gross burn is total cash out. Net burn is gross burn minus cash collected. Net burn determines runway.
• Use trailing 3-month average net burn, not a single month. This smooths volatility from annual payments, bonuses, and other one-time events.
• Break burn by department to identify where cash is most efficiently deployed. Protect high-efficiency departments when cutting.
• Annual billing creates uneven monthly cash collection; this is why trailing average is essential.
• Benchmark your burn rate against peers at your ARR stage, but adjust for vertical, geography, and go-to-market model differences.