Burn rate explained: definition, calculation, and optimisation for SaaS founders

Executive overview

Mismanaged burn rate is the leading cause of startup failure. Burn rate is simple: cash at month start, plus cash collected, minus cash spent. Divide cash in bank by burn rate to get runway in months.

Knowing exactly where cash goes — and whether each dollar returns more than a dollar — is the only lever that matters.

The burn rate formula

• Start with cash in bank at the beginning of the month
• Add cash actually collected from sales (not invoiced — cash received)
• Subtract cash paid out on expenses
• The result is your burn rate (negative = spending more than earning)
• Divide cash in bank by burn rate to calculate runway in months

Understanding the three expense buckets

• R&D: engineers and product development — longest lag before revenue impact
• Sales and marketing: the go-to-market machine — most direct link to cash coming in
• General and administrative (G&A): offices, infrastructure, legal, admin
• Most SaaS companies spend roughly 20% on R&D; the remainder should weight toward sales and marketing
• Knowing your top 20 vendors by spend each month reveals where money actually goes

Venture-backed vs bootstrapped burn patterns

• Venture-backed founders tend to overspend — pressure to deploy capital often overrides ROI discipline
• Bootstrap founders tend to underspend — hoarding cash leaves growth opportunity on the table
• Both problems share the same root: not understanding how money flows through the business
• Bootstrap founders with surplus cash can pay themselves directly; venture-backed founders are expected to reinvest for growth

Four ways to optimise burn rate

1. 13-week cash flow forecast — map cash out and forecasted cash in week by week; clarifies runway and forces trade-off decisions
2. Right-size the team — rough benchmark: $120K ARR per employee; audit whether headcount skews toward R&D at the expense of go-to-market
3. Audit the top 20 expenses — renegotiate, cut, or find lower-cost alternatives; inefficiencies are almost always present
4. Invest in go-to-market — the goal is $2 out for every $1 in; an efficient sales and marketing machine compounds: surplus reinvested generates more surplus