Online professional networking service LinkedIn is boosting the size of a follow-on stock offering, agreeing to sell $1.2 billion of its shares.

On Tuesday the Mountain View, Calif. company said that it planned to sell $1 billion of its stock in the offering. It said that the stock sale would help to increase its financial flexibility and strengthen its balance sheet.

LinkedIn said late Wednesday that the offering of about 5.4 million shares will be priced at $223 a piece. The company is giving the underwriters a 30-day option to buy up to an additional 807,174 shares.

LinkedIn plans to use the offering's proceeds for general corporate purposes like expanding its product development and sales organizations, expanding its international businesses. It may also use some of the proceeds for acquisitions or investments.

LinkedIn Corp. shares have more than doubled in value over the last year, and they reached an all-time high of $247.98 on Aug. 26. The stock gained $5.32, or 2.2 percent, to $244.25 in midday trading on Thursday.