Public Float
Public float is the number of a company's shares available for trading by the public, excluding shares held by insiders and other restricted holders.
Float, or public float, is the part of a company's shares that can actually change hands in the market. It is shares outstanding minus shares held by insiders such as executives, directors and controlling shareholders, as well as shares under lock-up or other restrictions.
Float matters because it shapes how a stock trades. A company with a small float has relatively few shares available, so strong buying or selling can move the price a lot. Low-float stocks tend to be more volatile and are more prone to short squeezes. A large float usually means smoother, more liquid trading.
Many major stock indices, including the S&P 500, use float-adjusted market capitalization to weight their members. This means a company with a large insider stake gets less index weight than its total market cap would suggest.
Example: a company has 100 million shares outstanding. Its founder owns 40 million, and 5 million are restricted employee shares. The public float is 55 million shares. If 11 million shares are sold short, short interest equals 20% of float.