(Bloomberg News) How much does it take to feel wealthy these days? For many millionaires, it's about $7.5 million, according to a survey by Fidelity Investments.

"Wealth is relative, and to some extent the more you have the more you realize how much more you need," said Sanjiv Mirchandani, president of National Financial, a subsidiary of Boston-based Fidelity, that provides clearing and custody services to broker-dealers, in an interview before the survey's release today.

The more than 1,000 households surveyed had an average of $3.5 million in investable assets. About 42% said they don't feel wealthy, saying they would need about $7.5 million to feel rich. The 58% of respondents who said they do feel wealthy were younger on average and have a greater number of remaining years in the workforce, said Mirchandani.

A 65-year-old millionaire is "looking at potentially the loss of a paycheck as they retire, and 30 years in retirement, with inflation on the horizon," said Mirchandani. "So they kind of go 'Well, $3.5 million, $4 million, isn't what I thought it would be. I'd like to have more.'"

There are about 5.5 million U.S. households with at least $1 million in assets, or about 5% of the population. Millionaires control 56% of the country's wealth, according to Fidelity, which is the second-largest U.S. mutual-fund company after Vanguard Group Inc. Household wealth was $56.8 trillion at the end of 2010, according to the Federal Reserve.

The survey found millionaires' outlook for the future is the most positive it's been in at least four years.

Turning a Corner

"They're beginning to feel that perhaps we're turning the corner on a more consistent basis," said George Walper Jr., president of Chicago-based Spectrem Group, a consulting firm that tracks attitudes among millionaires.

About 56% of registered investment advisors, who manage or advise individual investors' money, are bullish on the stock market's prospects over the next six months, according to a January survey by San Francisco-based Charles Schwab Corp. Of the advisors surveyed, 23% said they're providing reassurance to their clients about reaching their investment goals, down from 49% in January 2009.

About 83% of millionaires surveyed by Fidelity said the financial crisis didn't shake their confidence in investing, and a majority said a primary goal for their money is preservation of capital, rather than growth.