Pfizer's unit Zoetis plans to sell 86.1 million shares at between $22 and $25 each in an initial public offering that could value the animal health business at as much as $12.5 billion.
At the top-end of the expected range, the offering would raise about $2.2 billion.
The Wall Street Journal reported last month that the Zoetis IPO was likely by January or February, and that it could raise about $4 billion.
Pfizer said in June last year that it planned to separate its animal-health unit, which sells medicines, vaccines and other products for livestock and pets, into a standalone company.
The unit reported revenue of $3.16 billion, or about 7 percent of Pfizer's overall revenue, for the nine months ended Sept. 30, 2012.
Zoetis had filed with regulators in August a placeholder amount of up to $100 million, as the largest U.S. drugmaker looked to spin off the unit and narrow its focus on its core prescription drug business.