President Gianni Infantino's favored plan — for 16 three-team groups with the top two advancing to a round of 32 — was unanimously approved Tuesday by the FIFA Council.
It meets Infantino's election pledge of a bigger and more inclusive World Cup going beyond European and South American teams, which have won all 20 titles.
"We have to shape the football World Cup of the 21st century," said Infantino, who also promised funding increases for FIFA's 211 member federations at his election last February.
With 80 matches instead of 64, FIFA forecasts the equivalent of $1 billion extra income at current rates from broadcasting and sponsor deals, plus ticket sales, compared to $5.5 billion revenue forecast for the 2018 World Cup in Russia.
FIFA projects an increased profit of $640 million despite some extra operating costs and prize money for teams.
FIFA's six continents should find out by May how many extra places they will each get.
"No guarantees have been made," Infantino said. "The only sure thing is that obviously with 48 teams everyone will have a bit more than they have today."
UEFA wants 16 European teams at the tournament, which is strongly favored to be played in North America. The CONCACAF region has not hosted the World Cup since the 1994 tournament in the United States.
American, Canadian and Mexican soccer leaders have had informal talks about a co-hosting bid.
FIFA members are scheduled to pick the host in May 2020, though there could be little competition in a process Infantino said must be "bullet-proof" to meet all integrity rules.
Africa and Asia could be winners in a bigger World Cup with up to nine places each. They had only five and four teams, respectively, at the 2014 World Cup in Brazil.
Still, FIFA said it expects the standard of soccer to drop compared to the 32-team format locked in for the next two World Cups in Russia and Qatar.
The "absolute quality" of play, defined by high-ranked teams facing each other most often, is achieved by 32 teams, FIFA acknowledged in a research document sent to members last month. It made 10,000 tournament simulations to reach that conclusion.
Instead, Infantino wants to create fervor and months of anticipation back home in the 16 extra nations which would qualify, some probably making their World Cup debut. FIFA has pointed to Costa Rica, Wales and Iceland as examples of teams which overachieved at recent tournaments.
FIFA must break with soccer tradition to make its new format work after an original 48-team plan — with an opening playoff round sending 16 "one-and-done" teams home early — was unpopular.
Instead, three-team groups will replace the usual groups of four to create simple progress to a knockout bracket. However, it leaves one team idle for final group games and could risk collusion between the other two teams.
FIFA said it could guard against result-rigging by introducing penalty shootouts after group games that end in draws.
Infantino said a decision could wait until 2024 to agree on competition rules.
Despite the 16 extra games, FIFA believes the current maximum of stadiums needed will stay at the 12 used by Brazil and Russia. However, the demand for more training bases and hotels means developed countries would be better equipped to win future hosting contests.
North America is the strong favorite for 2026 because European and Asian countries are blocked by a FIFA rule excluding continents which hosted either of the two previous tournaments. Russia will host the World Cup next year and Qatar in 2022.
South America has been focused on a centenary tournament including original 1930 host Uruguay, and African nations are seen as lacking existing capacity and unlikely to fund multi-billion dollar infrastructure spending.
(AP)