Internet Brands Inc., an El Segundo Internet media firm, said on Monday that it will be acquired by a private equity firm in a deal valued at roughly $640 million.

Hellman & Friedman Capital Partners, which has offices in San Francisco, New York and London, will pay $13.35 in cash for each share of Internet Brands common stock, more than 46 percent premium over its Friday closing price. Debt financing commitments have been arranged with Bank of America N.A., BMO Capital Markets, GE Capital and RBC Capital Markets.

Internet Brands is a spinoff of Pasadena Internet incubator Idealab and operates several dozen consumer sites, including CarsDirect.com, Gardens.com and DoItYourself.com. Idealab still owns about 19 percent of outstanding shares, has 64 percent voting power and has agreed to the deal. The transaction is expected to close in the fourth quarter following a shareholder vote.

“We are very happy for our stockholders – this is a great outcome. And we’re excited about continuing to build our business with a great new partner,” said Internet Brands Chief Executive Bob Brisco in a statement.

Shares were up $4.07, or nearly 45 percent, to $13.18 in midday trading on the Nasdaq.