List of index and the percent over total US stock market. source from wikipedia and the offical websites.

Index Market Cap (%) Comment
S&P 500 80%
S&P 400 7%
S&P 600 3%
S&P 1500 90%
S&P 100 51%
Russell 3000 98%
Russell 1000 88.2% 90% of Russell 3000
Russell 2000 9.8% 10% of Russell 3000
Russell Top 50 39.2% 40% of Russell 3000
Russell Top 200 68% 63% of Russell 1000 (wiki), 68% (official)
Russell MidCap 27.3% 31% of Russell 1000, 800 smallest companies in Russell 1000
Russell Microcap < 3% 1000 smallest securities in Russell 2000

Table: Major index and their market cap.

Some numbers might be different from the offical website. For example, as of 2020-03-01, Russell Top 200 FactSheet says:

The index represents approximately 68% of the US market.

However, wiki say

Russell Top 200 represents 63% of total market capitalization in the Russell 1000 Index.