How much runway should a B2B SaaS company have?

Capital, cash and fundraising · Answered by Golden Section from more than 400 B2B software companies observed

The Golden Section answer

Hold enough cash to absorb a surprise churn or a customer paying months late without changing course. For most companies that means six months of operating expense at the forecast trough, or access to a line of credit or debt facility, such as Golden Section Lending, that lets you adjust the P&L and reach profitability if you have to. More than that is inefficient: cash from debt costs 15% to 20% a year, and cash from equity costs 50% or more. So measure runway to the month the company funds itself, not as a fixed count. If the forecast reaches breakeven with the reserve intact, 12 months can be plenty; if it depends on a raise, allow twice the time founders expect. Build it from a monthly cash flow forecast with collections timing in it.

The decision rule

Runway is enough when the monthly forecast reaches self-funding, or a closed financing, with six months of operating expense in reserve or an undrawn facility that covers the same shock. Cash beyond that should have a job, because idle equity is the most expensive money on the balance sheet. If the forecast cannot get there, cut or start raising now, while the reserve is still there to negotiate with.

Usually ready when

  • A reserve or facility covers a surprise churn or late payment
  • The forecast reaches breakeven before the reserve is touched
  • The forecast is updated with actuals every month
  • Collections timing is modeled, not assumed

Probably too early when

    The numbers

    MetricValueWhat it meansSource
    Operating reserve6 months of operating expensecash held back at the forecast trough and never spent on the planour general runway standard, which an undrawn debt facility can stand in forGolden Section, publishedGrowth Capital Without Heavy Dilution
    Fundraising timelinedouble your estimatetime from first meeting to cash in the bankMistake 69 on the published mistakes listGolden Section, publishedThe B2B Software Mistakes List
    Debt facility sizingsized to 12 monthsborrowing against what a proven motion returnswith covenants set on trailing performance and a modeled downsideGolden Section, publishedCombining Equity and Non-Dilutive Debt
    Cost of holding excess cash15%–20% from debt; 50%+ from equityannual cost of the capital that funds cash beyond the reservewhy a cushion larger than the shocks require is inefficientGolden Section operating viewGolden Section operating view

    Why

    Runway is a forecast, not a division problem. A company with $3M in the bank and $150K of monthly burn does not have 20 months if its customers pay net-45, its payroll runs every two weeks, and half its revenue bills annually in the first quarter. The real figure comes from a cash flow forecast built with collections timing, updated monthly with actuals, and owned by the founder.

    The reserve exists because forecasts are wrong in the same direction. A large customer churns without warning, another pays 60 days late, a hire costs more than planned. Six months of operating expense at the trough, or a facility such as Golden Section Lending, is what lets a bad quarter stay a bad quarter while you adjust the P&L.

    The opposite error is quieter. Cash held far beyond what those shocks require is not free: debt costs 15% to 20% a year and equity 50% or more. Running short does its damage earlier, though, through discounts to pull deals forward and terms accepted to make payroll. We would rather see a founder cut early with the reserve intact, and receivables discipline is the cheapest runway most companies have.

    Illustrative scenario

    A company at $3M in annual revenue holds $3.6M in cash with net burn of $150K a month, which reads as 24 months of runway. Its operating expense runs about $300K a month, so a six-month reserve is $1.8M. That leaves $1.8M the plan can actually spend, or 12 months at current burn, and the forecast reaches breakeven in month 15. The founder has three honest options: trim burn to about $120K a month so breakeven arrives before the reserve is touched, put an undrawn facility in place to stand in for part of the reserve, or open a financing conversation now, with 12 spendable months left rather than six. The figures are invented.

    When this does not hold

    A company with committed financing in the bank, or an undrawn facility on terms it has modeled, can hold less cash, because the facility is the reserve. Seasonal verticals should size the reserve to the seasonal trough rather than an average month.

    What to do on Monday

    1. Rebuild runway from the monthly cash flow forecast, with collections timing, rather than from the bank balance.
    2. Compute six months of operating expense at the forecast trough and mark it as untouchable.
    3. Read off the spendable months and the month the company funds itself.
    4. If spendable months run out before self-funding, choose now between cutting burn and starting a financing.
    5. Put receivables over 30 days on this week's agenda.

    Mistakes founders make here

    From the Golden Section mistakes list, each paired with the play that prevents it.

    Mistake 142: Not proactively managing cash

    Runway is only real if burn and cash position are known at all times, not reconstructed when it gets tight.

    Mistake 136: Not changing the cash model

    A cash model left unchanged for two quarters overstates runway as reality drifts from the plan.

    Mistake 69: Underestimating the effort of fundraising

    Founders plan runway around a raise that takes half as long as it will.

    Mistake 127: Making costly business decisions based on investors soft commitment.

    Spending against a soft investor commitment turns a financing delay into a cash crisis.

    Plays we would run

    In the order we would run them. Each is on its own page, most with a free Excel template.

    Cash Flow Forecast

    Produces the real runway, trough and self-funding month.

    Accounts Receivable Process

    Pulls earned cash in sooner, the cheapest runway available.

    Budget Creation

    Ties spending to a realistic plan so burn matches what the forecast assumed.

    KPI Dashboard Creation

    Keeps cash, burn and runway in front of the leadership team every week.

    Executive plays Cash management sits with the founder, and the executive plays cover the forecast, budget and reporting that keep it honest.

    Questions this page answers

    Is 12 months of runway enough for a SaaS startup?

    It is enough if the forecast reaches self-funding inside those 12 months with a six-month operating reserve untouched. It is not enough if the plan depends on raising, because a raise that runs long, as most do, will leave too few months to negotiate from. In that case act on cost or financing now.

    How much cash should a SaaS company keep on its balance sheet?

    At least six months of operating expense at the lowest point in the forecast, or an undrawn facility that covers the same shock. Beyond that, cash should be assigned to a specific use, reinvested in a proven channel, or returned to shareholders; our equity model moves from building cash at 10% net profit toward regular dividends at 20%. Excess cash is expensive: 15% to 20% a year if it came from debt and 50% or more if it came from equity.

    Funding the next stage

    Golden Section Lending can serve as the reserve: an undrawn facility that covers a surprise churn or a late payer costs far less than holding the same cash raised as equity. Our lending starts at $1M ARR with 90%+ net revenue retention, and debt taken to cover a gap with no path to self-funding shortens runway, so we would fix the plan first.

    Growth capital lending →

    Reviewed by Dougal Cameron, CEO & Co-Founder on 2026-09-23. Golden Section observations are labeled separately from external benchmarks and illustrative arithmetic.