Hotel profit optimization company Duetto has taken $21 million in new funding to market its service worldwide.

Duetto sells subscriptions to its cloud-based software, which helps hotels sell all of their rooms for the highest possible profit.

Duetto does this by gathering and analyzing lots of disparate data sets — things like flight times, air traffic, weather patterns, and Internet hotel shopping behavior, co-founder Marco Benvenuti told VentureBeat. Based on this information, hotels can predict demand levels for a certain time period and set prices accordingly.

“While third-party intermediaries, such as Priceline and Expedia, continue to innovate and thrive, hotel profitability has remained stagnant,” Duetto CEO Patrick Bosworth said in a statement. “We are giving hotel owners, operators, and managers the tools they need to level the playing field and recapture revenue that is being lost on commissions.”

Duetto says it has signed hundreds of hotel properties since 2012 and is currently deployed in 16 countries. Early customers are seeing strong results with 10 to 20 percent revenue increases, more than doubling profitability in several cases, the company says.

To keep pace with demand, Duetto plans to continue its expansion into key markets throughout Europe and Asia.

Accel Partners led the round, with participation from previous investors Battery Ventures, Altimeter Capital, Thayer Lodging CEO Leland Pillsbury, and CEO Marc Benioff.