The Atlanta Falcons have joined a growing list of sports teams worth more than $1 billion, according to Forbes magazine’s annual calculation of NFL franchise values.

The Falcons are worth $1.125 billion, up 21 percent from a year ago, Forbes said in the study released Wednesday.

At that valuation, the team is worth more than twice as much as the $545 million that owner Arthur Blank paid for it in 2002.

Even so, Forbes ranks the Falcons as only the 21st most valuable NFL franchise and well below the league average of $1.43 billion.

The Dallas Cowboys are ranked as the most valuable at $3.2 billion, followed by the New England Patriots ($2.6 billion), Washington Redskins ($2.4 billion), New York Giants ($2.1 billion) and Houston Texans ($1.85 billion).

The study values 25 of the 32 NFL teams at $1 billion or more and the lowest-ranked team, the St. Louis Rams, at $930 million.

The valuations “are calculated using multiples of revenue that reflect each team’s current stadium economics with adjustments for pending new stadiums and renovations,” according to Forbes.

The Falcons’ new $1.2 billion retractable-roof stadium is under construction in downtown Atlanta and slated to open in 2017.

The Falcons are responsible for most of the cost of building the stadium. Bonds backed by Atlanta hotel-motel taxes will pay $200 million toward construction, and hundreds of millions of additional hotel-motel tax dollars will go into the stadium over 30 years for financing, maintenance and operating costs.

Last year, Forbes valued the Falcons at $933 million, which ranked 26th among NFL teams at the time.

Earlier this year, in its annual calculation of Major League Baseball franchise values, Forbes said the Braves are worth $730 million.