Blackbaud, the Daniel Island-based software company, has reached an agreement to acquire Convio, an Austin, Tex.-based software company that also helps nonprofits connect with their donors, the companies announced Tuesday morning.

Under the terms of the agreement, Blackbaud will pay $16 for each of Convio's outstanding shares, a 49 percent premium over Friday's closing price of $10.75 per share and based on a company valuation of $275 million, according to the news release. Convio's stock price jumped to Blackbaud's proposed buying price Tuesday morning.

While the acquisition has been approved by both companies' boards, the consummation of the deal, which Blackbaud will fund with cash and debt, is contingent upon Convio shareholder approval and antitrust review.

Convio, which counts more than half of the top 50 U.S. charities among its more than 1,500 customers, specializes in software that enables nonprofits, through email and social media, to keep in touch with their supporters and maximize fundraising, according to the release. Its president and CEO Gene Austin will join Blackbaud and report to Blackbaud CEO Marc Chardon.

Blackbaud, about half of whose 2,200 employees are based at its local headquarters, offers a variety of software products to help nonprofits do their fundraising, marketing and finances. The 30-year-old company went public in 2004 and, in fiscal 2010, reported almost $30 million in profit on $327 million in revenue.

Chardon called the deal a "significant event for both companies."

"We fully expect that Convio's best-in-class, [software as a service]-based capabilities for large events, advocacy and federated organizations will enable Blackbaud to offer the industry's most diverse and flexible set of online capabilities on a global basis," Chardon said in the statement. "Moreover, the addition of Convio will broaden Blackbaud's application portfolio, enabling the combined company to offer a comprehensive set of multi-channel supporter engagement solutions to nonprofit organizations of all sizes."