An independent study from online consultancy firm Aim Group found that Craigslist's revenue has grown steadily since it first estimated its total in 2003 at $7m.
Peter Zollman, of Aim Group, said: "Craigslist is a stunning business success story, especially since it's run more like a community service than a for-profit business. And despite tremendous negative publicity and legal battles, its revenue keeps increasing at a remarkable pace."
A Craigslist spokeswoman said: "We are a privately held company and never comment on guesses of our revenue. Nor have we ever commented on any number bandied around in the past."
is an online classifieds website based out of San Francisco that lets users from nearly 600 cities around the globe post ads online for free.
From this, the company only charges a small fraction of its users.
In 18 US cities, Craigslist charges recruiters $25 per ad to post job listings, and $75 in San Francisco. In New York, the company charges real estate agents $10 to post apartment and house lettings.
It also requires a fee for its erotic services ads, recently changed to adult services after legal pressure in the US and the high-profile case of a masseuse who advertised on the site and was murdered by 'Craiglist Killer' Philip Markoff. Craigslist says the money made from adult services goes directly to charity.
Aim Group said that 80% of Craigslist's revenue comes from recruitment ads, with the rest coming from real estate ads in New York. The study said that New York listings contributed nearly $18m in revenue in 2009 and San Francisco $14m.
The revenue estimates were on the conservative side, said the study, which deduced the figure by counting the number of paid ads on the site for a month and generating an annual figure from that.