Jack Dorsey made $300m on Square

Jack Dorsey

Square's surge Thursday may make its CEO and co-founder Jack Dorsey forget all about Twitter's drubbing this year.

Shares of the mobile payment company soared 45 percent in their public debut, netting Dorsey a roughly $300 million paper gain. Dorsey — who currently heads both Square and Twitter — saw his net worth top $1.5 billion Thursday in stock value alone.

Square opened at $11.20 per share Thursday after pricing at $9 a share, below the company's initial expected range of $11 to $13 a share. The stock climbed to $13.30 a share by 1:45 p.m. ET .

At that price, Dorsey's more than 71 million shares were worth about $945 million. Taking away their value at the $9 per share IPO price, Dorsey made $305 million on Thursday alone.

At Twitter's price of $26.40 per share Thursday afternoon, Dorsey's stake in the social media company was valued at more than $575 million. Dorsey's stock in the two firms amounted to more than $1.5 billion on Thursday.

Dorsey's pay from the companies adds little to his net worth. He took in a salary of only $3,750 at Square last year, and currently makes nothing at Twitter.

Still, Dorsey does not plan to hold all of the shares he owns currently. In a filing with the Securities and Exchange Commission, he said he plans to give 40 million shares to a foundation that invests in artists and small businesses.

It was unclear whether the donated shares were subtracted from the stake disclosed to the SEC.