Revenue Doubled. The Bank Balance Didn't.
Picture a solo operator running a Smart Store — Naver's online marketplace platform — entirely on their own. Revenue is up nearly twofold from last year. Order notifications ping all day, and the sales chart keeps climbing up and to the right. Yet the bank balance at month's end has actually shrunk. Between stocking up on inventory ahead of time, ramping up ad spend, and waiting on delayed payouts, there's never a moment for cash to actually sit in the account. Come month's end, the same question resurfaces: why isn't there any money left?
Coupang's 10-K filing offers a useful answer to that question. Over five years, Coupang nearly doubled its revenue, but the cash it kept didn't grow anywhere near that pace. The scale is different, but the structure looks a lot like that Smart Store operator's bank account. This piece uses Coupang as a case study for learning how to read free cash flow margin.
Divide What's Left Over by Revenue
Free cash flow, or FCF, is the cash a company actually generates from operations minus what it spends on equipment and facilities — capital expenditures. It's different from the profit line on an income statement. Profit is a number computed under accounting rules; free cash flow is closer to the money that genuinely remained in the account during that period. Divide that figure by revenue and you get the free cash flow margin — a measure of how many cents of every dollar in sales actually ended up in hand.
Reading free cash flow margin well takes two precautions. First, always set it next to the revenue growth rate. If revenue is climbing while the margin shrinks, it means the business burns through more cash the bigger it gets. Second, ask where that cash came from. Cash a business generates on its own and cash left over from deferring investment look identical in the bank account, but they're fundamentally different. Deferred investment comes back as a bill the following year.
Where Coupang's Numbers Diverge
Coupang's revenue nearly doubled, from $18.4 billion in FY2021 to $34.5 billion in FY2025. Debt looks healthy too. The debt-to-equity ratio fell to 0.14x in FY2025 from 0.24x the year before, and long-term debt dropped from $988 million to $648 million. Taken this far, it reads like a model case of a company scaling up while paying down debt.
But free cash flow margin moved in the opposite direction. The margin, which stood at 7.4% in FY2023, slid to 3.3% in FY2024 and then to 1.5% in FY2025. FY2025's free cash flow of $522 million works out to just 1.5 cents for every dollar of the $34.5 billion in revenue. What's more, the cash that climbed as high as $1.8 billion in FY2023 turned out to be a temporary bump created by selectively holding back capital spending. Line up revenue, debt, and cash left over side by side, and this is where the story splits.
The company grew bigger and its debt shrank, yet the cash left over per dollar of revenue thinned from 7.4 cents to 1.5 cents in just three years. When revenue doubles but the cash left over doesn't keep pace, that business's underlying strength hasn't actually been proven yet. Profitability tells the same story. Return on equity fell from 34.1% in FY2023 to 3.8% in FY2024 and then 4.5% in FY2025. Carrying little debt and generating plenty of cash are recorded in different cells of a financial statement, and one cell looking good doesn't mean the one next to it does too.
Run the Same Math on Your Own Account
A Smart Store operator can run the identical calculation. Start with last month's actual deposits, then subtract what actually left the account — cost of goods, platform fees, ad spend, taxes. From what remains, subtract once more whatever got tied up in things that won't sell right away: camera equipment, a warehouse deposit, inventory bought in bulk ahead of time. Divide what's left by that month's revenue, and that's your business's free cash flow margin.
A single number doesn't tell the story on its own — three things need to sit alongside it: that same month's revenue growth rate, the margin trend over recent months, and a list of investments deferred that month. If revenue doubled but the margin was cut in half, growth is eating your cash. If a month's margin looks great because you put off buying equipment, that cash is borrowed cash. Feeling safe just because you carry no debt is the same trap. As Coupang shows, a company can carry little debt and still keep only a razor-thin margin of cash.
One Line to Write Down Today
Today, try opening your banking app, pulling last month's full deposit-and-withdrawal history, and writing down one line: cash left over divided by revenue. Next to it, write last month's revenue growth rate, and you've completed the first page of learning to read free cash flow margin. Everyone else can see the sales chart — but this one line, only the operator can write.
