The amount of common stock of a public company that is actually available for active trading in the public market. The calculation of a company's public float normally excludes securities held by officers, directors and affiliates of a company since officers and directors generally are not active traders. The public float also excludes securities that cannot be sold by agreement with the security holder. The smaller the public float, the less liquidity is available to someone seeking to sell stock. Many institutional investors (i.e., pension funds and mutual funds that buy large amounts of securities) will not purchase securities in a company whose public float is below a minimum size because the institutional investor will lack the ability to easily and quickly sell large amounts of securities.