What is a Stock Float? Definition, Formula, and Example
A stock's float is the number of shares actually available for public trading, equal to shares outstanding minus restricted shares held by insiders, employees, and controlling shareholders.
What is a Stock Float?
A stock's float is the count of shares that can actually trade on the open market. It equals total shares outstanding minus restricted and closely held shares: insider holdings, employee stock plan shares, locked-up pre-IPO stock, and strategic stakes that do not trade day to day. Float is the real supply of a stock. Two companies with identical market caps can have wildly different floats, and the smaller-float name will move faster on the same dollar volume because there is less inventory to absorb buying or selling pressure. Float is the denominator in short interest ratios, the driver of short squeezes, and a primary filter for day traders.
How Float is Calculated
The formula is direct:
Float = Shares Outstanding - Restricted Shares - Closely Held Shares
Shares outstanding comes from the cover of the most recent 10-K or 10-Q filed with the SEC. Restricted shares include unregistered shares from private placements and shares under lock-up agreements. Closely held shares include insider positions reported on Form 3/4/5 filings and large strategic holders. Data providers estimate float by subtracting these from outstanding; the SEC filings themselves are the authoritative source. Related derived metrics include float percentage (float / shares outstanding) and float utilization, which measures how much of the float is currently sold short.
Worked Example
Consider a small-cap, call it the profile of a name like MARA in its earlier days: 200 million shares outstanding, 40 million held by insiders and restricted holders, leaving a float of 160 million shares, or 80% of outstanding. Now take a recent IPO with 200 million shares outstanding but 170 million locked up or insider-held: float is only 30 million shares, 15% of outstanding. If short sellers borrow and sell 9 million shares of the IPO name, short interest is 4.5% of outstanding but 30% of float. That second number is what matters. A 30% float-short name needs only modest buying pressure to force covering into a thin supply of shares, which is the mechanical setup behind squeeze moves in low-float stocks.
When Traders Use It
Day traders filter for low-float names, typically under 20 million shares, because small supply plus a volume catalyst produces the largest percentage moves. A low-float stock with a press release and 10x relative volume can reprice 50% in an hour because there simply are not enough shares for sale at each level. Short sellers use float to size risk: shorting a heavily shorted low-float name exposes you to a squeeze, and days to cover tells you how long covering would take. Long-term investors use float to understand index weighting, since most modern indices are free-float adjusted, and to gauge how much insider alignment exists. You can track float-short and utilization leaders on the squeeze leaderboard.
Limitations and Common Misconceptions
Float is an estimate, not a filed number. Different providers disagree because the classification of "closely held" requires judgment, and float changes when lock-ups expire, insiders sell, or secondaries price. A low float cuts both ways: the same supply scarcity that produces 80% squeezes produces 60% dumps when the bid disappears, and spreads in low-float names are wide and slippage is severe. Float also ignores borrow availability: a 15% float-short stock with easy borrow is a different animal than one with a 40% borrow fee. Finally, float is static while the squeeze dynamic is flow-driven; watch live volume against float, not float alone.