Free cash flow is operating cash flow minus capital expenditure — the real cash a business keeps to fund growth, repay debt, or hold.
Free cash flow = operating cash flow − capital expenditure
A SaaS business generates £2,400,000 of operating cash flow in a year and spends £300,000 on capital expenditure.
£2,400,000 − £300,000 = £2,100,000 free cash flow
Free cash flow is what is left in actual cash after a business has paid for its operations and its capital expenditure. It starts from operating cash flow — the cash generated by the day-to-day business — and subtracts capex, the money spent on long-lived assets. Unlike profit, which is shaped by non-cash items and accounting choices, FCF is a hard measure of the cash a company truly produces.
For SaaS, FCF often looks better than profit, and the reason is billing. When customers pay for an annual plan upfront, the cash lands immediately while the revenue is recognised across the year — so a company can be unprofitable on paper yet free-cash-flow positive, because deferred revenue and upfront collection pull cash forward. This is why the Rule of 40 on an FCF basis flatters many SaaS relative to the EBITDA view.
FCF is the metric that ultimately decides whether a business can fund itself. Positive FCF means operations throw off more cash than they consume, removing the dependence on outside capital; negative FCF means the company is still consuming cash and relying on its balance sheet or fresh funding. It is the cash-flow truth behind burn rate and runway.
Free cash flow is the closest thing to ground truth about a company's financial health, because cash is harder to massage than profit. It determines whether a business can self-fund its growth or must keep raising, and for SaaS it often tells a more favourable story than earnings — upfront annual billing pulls cash forward, which is why FCF margin is the lens many investors trust most for a subscription business.
FCF margin (FCF ÷ revenue) is the comparable figure: the median public SaaS company runs only about a 5% FCF margin (t2d3, 2025), while world-class names clear 20%+ — Veeva near 40% and ServiceNow in the high-20s to low-30s (saasdb, 2025). High-growth companies often run negative FCF by design as they invest ahead of revenue, so judge it against growth stage and the Rule of 40.
Profit is an accounting figure shaped by non-cash items and recognition rules; FCF is the actual cash left after operations and capex. A SaaS can be unprofitable yet free-cash-flow positive when annual plans are billed upfront and collected ahead of recognition.
Because upfront annual billing pulls cash forward. The full year's cash arrives at signing while revenue is recognised monthly, so the cash position runs ahead of the income statement — reflected in a growing deferred revenue balance.
Yes. FCF turns negative whenever capex and operating outflows exceed the cash operations bring in. For an early or fast-scaling SaaS it is often negative by design while it invests ahead of revenue, so it is not automatically a red flag — what matters is the trend toward positive and the runway to get there. Persistent negative FCF with no path to break-even is the warning sign.
Start with net income, add back non-cash charges like depreciation and amortisation, adjust for the change in working capital to get operating cash flow, then subtract capital expenditure. In short: FCF = net income + non-cash charges − change in working capital − capex. For SaaS, a rising deferred revenue balance is the working-capital swing that pushes FCF above net income.
Unlevered FCF (free cash flow to the firm) is the cash available to all investors before any debt payments, so it ignores interest and is used in DCF valuations. Levered FCF (free cash flow to equity) is what remains after interest and debt repayments — the cash that actually belongs to shareholders. Unlevered is usually the higher figure because it sits above interest and debt payments.
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