A company might have a billion shares in issue, but that does not mean a billion shares are available to trade. Some are held by founders, governments or strategic investors who rarely sell. The shares left over, the ones that can realistically change hands, make up the free float. It is a quiet number that shapes index weightings, liquidity and how violently a share price can move.
What counts as free float
Free float is the portion of a company’s shares held by investors who are likely to trade them. It usually excludes holdings by directors and founders, other companies with strategic stakes, governments, employee share trusts and shares locked up after an IPO.
It is usually shown as a percentage of total shares. A company with 100 million shares, of which 30 million are held by its founding family, has a free float of 70%.
Why index providers care
Major index providers, including FTSE Russell and MSCI, weight companies by free-float market value rather than total market value. A company with a large market value but a small free float will have a smaller weight in the index than its size suggests.
This matters because trillions of pounds track these indices through passive funds. When a free float changes, for instance because a major shareholder sells down a stake, the company’s index weight can rise. Index funds then have to buy more shares, which can support the price around the rebalancing date. The London Stock Exchange’s rules for premium listings have historically required a minimum free float, and FTSE applies its own free-float thresholds for index eligibility.
Liquidity and volatility
A small free float usually means fewer shares changing hands each day. That can lead to wider spreads and bigger price moves on modest buying or selling. Shares with a tight free float can be prone to sharp spikes, especially if many investors are short and need to buy back shares at the same time, a setup that can fuel a short squeeze.
A large free float generally means deeper liquidity and steadier trading, which is one reason large institutional investors prefer it.
When free float changes
Several events can change a free float. A large shareholder may sell part of a stake through a placing. A company may issue new shares, or buy back and cancel existing ones. Lock-up expiries after an IPO release shares that were previously restricted. A takeover bidder building a large stake reduces the float.
Each change can have knock-on effects, from altered index weights to shifts in daily volume.
What traders look for
Traders consider free float when judging how a share might behave. A low float combined with heavy short interest or a strong news story can produce dramatic moves in both directions. Index rebalancing announcements that include free-float changes can create predictable buying or selling pressure on specific dates.
It also helps with position sizing. In shares with a small free float, large orders can move the price against the trader, making entry and exit more expensive than the quoted spread suggests.
Limits and caveats
Free float figures are estimates. Data providers may use different rules about which holders count as strategic, so the number can vary between sources. Ownership disclosures are periodic, so a float figure may be out of date.
Our assessment is that free float is an underrated part of understanding any share, particularly smaller companies and recent listings. It helps explain why some shares move far more than others on similar news and why index changes can cause sudden demand. The key things to watch are major shareholder sales, lock-up expiries and index review dates. If you want a clearer view of how you assess shares and size positions, our free trader assessment is a good next step.
