A Stock's Market Cap Can Be Huge While Almost None of It Trades Freely. Free Float Is the Number That Reveals the Gap
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5 min read
PT Bayan Resources Tbk (BYAN) has a market cap of roughly Rp405 trillion as of 24 September 2026, one of the largest of any energy company on the IDX. Only about a fifth of that company is actually available for an ordinary investor to buy. The rest sits with a small number of large, controlling shareholders who are not selling into the open market. A company's market cap tells you what the whole business is worth on paper. It tells you almost nothing about how much of it you can actually trade. Free float is the number that does.
Market cap is simple arithmetic: current share price multiplied by total shares outstanding. It answers "how much is this whole company worth right now, if every single share traded at today's price." It says nothing about who holds those shares or whether they are for sale. A founder's stake, a government's stake, and a share sitting in your own brokerage account all count identically toward market cap, even though only one of those three is actually going to hit the market on an ordinary trading day.
Free float measures something narrower: the shares actually available for public trading, after stripping out the ones that are not realistically going to change hands. Under IDX's own Exchange Regulation No. I-A, effective 31 March 2026, a share only counts as free float if it is held by a shareholder owning less than 5% of the company, and only if that holder is not the controlling shareholder, an affiliate of the controller, or a member of the board of commissioners or directors. The 2026 update also excludes shares held by venture capital or private equity firms from the free float count entirely, regardless of the size of their stake, and excludes any shares still under a transfer restriction. A stock can have thousands of small public shareholders and still show a low free float percentage, because the definition is about who is excluded, not just who holds the rest.
This is also why free float is a completely different question from the one NetWort's own explainer on the IHSG's free-float weighting answers. That post covers how the index itself uses free float to decide how much weight one stock gets inside the IHSG. This one is about a single stock's own free float on its own terms, whether or not it is even in the index.
BYAN is a concrete case of the gap. The company has 33,333,335,000 shares outstanding in total. As of the end of April 2026, its free float stood at 21.27%, or 7,089,564,830 shares, comfortably above BEI's current 15% minimum free float requirement. The remaining roughly 79% sits with Low Tuck Kwong, his family, and other large, related holders who are not part of the tradable float at all.
That concentration became visible in a very literal way just over a week before this was written. On 16 September 2026, Low Tuck Kwong and Elaine Low signed a Conditional Share Sale and Purchase Agreement to sell 10,000,000,500 shares, about 30% of the entire company, to PT Jhonlin Baratama, part of businessman Andi Syamsuddin Arsyad's (known as Haji Isam) Jhonlin Group. Based on BYAN's Rp11,525 closing price the day before the deal became public, that block was worth roughly Rp115 trillion at market price, though the companies did not disclose the actual price agreed between the parties. When the news broke, BYAN's share price jumped 19.96% in a single session, to Rp13,825, hitting the exchange's daily upper trading limit (Auto Reject Atas). None of those 10 billion shares came from, or went into, the public float. It was a private transfer between two large, controlling-type holders, the exact kind of holding free float is specifically designed to exclude.
A stock with a small free float relative to its market cap tends to move harder on comparatively little trading volume, because there are simply fewer shares circulating to absorb buy and sell orders. BYAN's own near-20% single-day jump on a large concentrated-ownership headline, rather than on a change to its coal business, is one visible version of that dynamic. It is also why regulators keep raising free float minimums in the first place: IDX's own 15% requirement, effective 31 March 2026, replaced a lower 7.5% threshold specifically to improve liquidity and align Indonesia more closely with what international index providers like MSCI look for. Existing large-cap companies still short of the new bar get a phased runway, reaching 12.5% free float by 31 March 2027 and the full 15% by 31 March 2028, rather than an immediate cutoff.
A large market cap alone does not tell you how easily you could buy or sell a meaningful position without moving the price yourself, and it does not tell you how concentrated the ownership sitting above you actually is. Before treating a big number as a sign of stability, check the company's own free float disclosure, not just its market cap. You can track BYAN's own price history and volatility on its NetWort asset page, including how sharply single sessions like 18 September 2026 show up against its calmer trading days.