Shares of Realogy Holdings Corp., the real estate brokerage company backed by Apollo Global Management LLC, fell sharply Tuesday after the company said it plans a secondary stock offering and estimated sales below analysts’ forecasts.

Realogy plans to offer 35 million shares held by Apollo, the Parsippany, New Jersey-based company said in a statement Tuesday after the close of regular trading. Apollo, the private- equity firm started by Leon Black, will own about 30.4 million shares after the sale if underwriters don’t exercise an option to buy additional stock.

Realogy, which owns the Century 21 and Coldwell Banker brands, expects to report first-quarter revenue of $950 million to $960 million, the company said in a separate statement. Seven analysts had an average estimate of $997.1 million, according to data compiled by Bloomberg. Realogy projected a net loss of $69 million to $78 million.

The shares fell 7.4 percent to $41.50 at 7 p.m. New York time. The stock has gained 65 percent since the company’s initial public offering on Oct. 10. The biggest one-day loss was 4.1 percent on April 3.