Free Cash Flow Explained: The Number Hardest to Fake

Think about your own household for a second. Your salary lands on the first of the month — that's your "profit." But you can't spend all of it. Rent, groceries, the electricity bill, the kids' fees: that's the cost of running the house. And once a year the monsoon finds a crack and you have to fix the roof — a big, lumpy, unavoidable cheque. Whatever is genuinely left in your pocket after running the house and fixing the roof — that, and only that, is money you can actually save, invest, or give away.

A business is no different. Its "salary" is profit. Running the house is its operating costs. And fixing the roof is capital expenditure — capex — the money it must spend on new plants, machines and equipment just to keep earning. Free cash flow is what's left after both. It is the single most honest number a company produces, and learning to read it is the skill this article is about.

Free cash flow, in one line

Here is the whole formula, and it really is this simple:

Free cash flow (FCF) = cash from operations − capital expenditure (capex).

Cash from operations (often "operating cash flow" or CFO) is the actual cash the business collected from customers, minus the cash it paid suppliers and staff — real money in the bank, not an accounting promise. Capex is the cash spent on the roof: factories, machines, warehouses, the physical stuff the business needs to keep going. Subtract one from the other and you get the cash the owners are truly free to use — to pay dividends, buy back shares, pay down debt, or fund the next expansion.

Profit, by contrast, is an opinion. It's calculated under accounting rules that involve dozens of judgement calls — when to book a sale, how fast to depreciate a machine, how much of a doubtful debt to provide for. Cash flow is a fact. The bank balance either went up or it didn't. That is why FCF is the number hardest to fake: you can flatter profit with clever entries for a while, but you cannot conjure cash that isn't there.

A real company: where the cash actually lands

Start with Apple. This is a worked example, not a view on the stock. In fiscal 2025 Apple generated $111.5 billion of operating cash and spent $12.7 billion on property, plant and equipment. Subtract the second line from the first and free cash flow was about $98.8 billion (Apple 2025 Form 10-K).

Read that in owner terms. Apple kept almost 89 cents of every dollar of operating cash after physical capex. Its products take immense design and supply-chain work, but Apple does not have to build another utility-scale network every time it sells another phone or service subscription. Most of the operating cash comes through the business rather than hardening into new plant.

The same number, the opposite story: when the roof eats the rent

Now meet the contrast, because the lesson only sticks when you see both sides.

Now put Apple beside NextEra Energy, whose utilities and power-generation businesses have to build the system before they can earn from it. NextEra generated $12.5 billion of operating cash in 2025. Florida Power & Light alone spent $8.7 billion on capex, while NextEra Energy Resources recorded another $15.3 billion of independent-power and other investments (NextEra Energy 2025 Form 10-K).

This is where the apparently simple FCF formula needs judgment. Subtract only the line explicitly labelled FPL capex and about $3.8 billion remains. Treat the power projects NextEra Energy Resources builds as part of the capital required to grow the company, and investment spending exceeds operating cash. Neither reading says the investment is bad. It says an owner cannot stop at net income or at a website's precomputed FCF field; in an asset-building business, you must inspect what the investing lines actually buy.

High capex isn't bad — but "good" capex earns its keep

It's tempting to leave here thinking "low capex good, high capex bad." That's too crude, and an honest owner says so.

A great deal of capex is the best money a company can spend. When a business reinvests a unit of capital and it comes back earning a high return, heavy capex is building the future, not leaking cash. The asset-turnover trend helps show whether the expanded base eventually produces more sales. The right question is never "is capex high?" It's: does the cash poured into the roof come back as more cash later? A company spending hard while free cash flow grows is compounding. One spending hard while FCF stays flat or negative is, quietly, on a treadmill — running fast just to stand still. (The companies here were chosen to teach the contrast cleanly; the lesson is in the pattern, not in singling one out.)

This is also why one year of FCF tells you little. Capex is lumpy: a company might build a big plant this year and almost nothing for the next three. Read FCF across several years, not one snapshot — does it trend up as the business grows, or does it keep getting swallowed? Pair it with the working-capital trend, because receivables and inventory can consume cash before capex even begins.

The grown-up version: Buffett's "owner earnings"

If this idea feels important, that's because the best investor alive built his definition of value on it. In his 1986 letter to shareholders, Warren Buffett described what he calls owner earnings — essentially reported earnings, plus non-cash charges like depreciation, "less (c) the average annual amount of capitalized expenditures for plant and equipment, etc." that the business needs to hold its position (Berkshire Hathaway, 1986 letter). That's free cash flow, in spirit: profit, adjusted back to cash, minus the capex needed to stay competitive.

And Buffett is refreshingly honest about the catch. That capex figure, he wrote, "must be a guess — and one sometimes very difficult to make." You won't get a perfect number; the right capex to subtract (just enough to maintain the business, versus extra to grow it) is a judgement. But, he insisted, "we consider the owner earnings figure, not the GAAP figure, to be the relevant item for valuation purposes." A rough cash number beats a precise accounting one. Approximately right beats exactly wrong.

How to read it without a finance degree

You don't need to model anything. Open the company's cash-flow statement — it's in every annual report and every results filing — and do three things:

1. Find "net cash from operating activities." That's your starting cash, the rent collected.
2. Find capex — usually "purchase of property, plant and equipment" under investing activities. Subtract it. What's left is free cash flow.
3. Do it for the last five years. Is FCF positive, and growing roughly with the business? Or does profit keep rising while cash never seems to arrive?

That last gap — profit going up, cash flow flat — is the most useful warning in all of investing, and it's exactly the kind of pattern an owner wants flagged across a whole portfolio rather than dug out one filing at a time.

Inve's US earnings-call research records management's capex plans when disclosed, with the figure, period, speaker and source quote. Put that plan beside the next 10-K cash-flow statement; the call explains the spend, while the filing shows what left the bank. The companion guide to reading an earnings-call transcript shows how to separate a quantified plan from promotional language.

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