Fidelity Investments has launched a service to help retail brokers determine how profitable it would be for them to leave their brokerage house and hang out their own shingle.

The online calculator is a way for Fidelity to boost its revenue from an increasingly important business -- providing support services to independent brokers.

With the top brokerages involved in mergers -- like Morgan Stanley's new Smith Barney joint venture with Citigroup Inc , or Merrill Lynch's purchase by Bank of America Corp -- industry observers have predicted a wave of brokers would leave the big players to open their own boutique firms.

Fidelity is one of the largest players in providing services to these brokers. The 3,500 independent advisors it supports oversee $370 billion in client assets.

Fidelity's new service, called Transition Solutions, calculates the income and expenses for a broker running his or her own firm over a 10-year period, based on the most common business models for independent investment advisors.

The Boston-based investment management firm has recruited 170 brokers to its independent advisor services through the first nine months of this year, it said, including Wayne, Pennsylvania-based Stillwater Capital Advisors, with $325 million in assets under management.

(Reporting by Joe Rauch; Editing by Lisa Von Ahn)