The S&P SmallCap 600 Index is a stock market index established by S&P Global Ratings. It covers roughly the small-cap range of American stocks, using a capitalization-weighted index.
To be included in the index, a stock must have a total market capitalization that ranges from $1.2 billion to $8 billion. These market cap eligibility criteria are for addition to an index, not for continued membership. As a result, an index constituent that appears to violate criteria for addition to that index is not removed unless ongoing conditions warrant an index change.
Additionally, same as S&P 500 and S&P 400, there is a financial viability requirement. Companies must have positive as-reported earnings over the most recent quarter, as well as over the most recent four quarters.
As of 30 January 2026, the index's median market cap was $2.25 billion and covered less than three percent of the total US stock market capitalization. These smallcap stocks cover a narrower range of capitalization than the companies covered by the Russell 2000 Smallcap index, which range from $169 million to $4 billion, excluding some of the smallest companies.Wikipedia