If 1D sells out all 3 shows at the Rose Bowl, that'll be about 270K seats sold. The Bowl normally seats 93K, but I'm just gonna remove about 3K a show just to make it even. The numbers on that would be insane. Could come out to around 20-21M from those 3 shows alone.
I don't normally do this research, so watch me be way off, but just imagine.
Also, tonight is their two night stint at Soldier Field which (if their sold out will be about 120K seats, equaling out to like 10M? I would assume.
Let me just make a little chart with my predictions:
August 29 + 30 - Soldier Field (Chicago, IL) = 10M
September 11, 12 + 13 - Rose Bowl (Pasadena, CA) = 20M
September 16 - University of Phoenix Stadium (Phoenix, AZ) = 4.5M
September 19 - Sun Bowl (El Paso, TX) = 4M
September 21 - Alamodome (San Antonio, TX) = 4.5M
September 23 - BOK Center (Tulsa, OK) = 500K
September 25 - Mercedes Benz Superdome (New Orleans, LA) = 5M
September 27 + 28 - PNC Music Pavilion (Charlotte, NC) = 3M
October 1 - Georgia Dome (Atlanta, GA) = 5M
October 3 - Raymond James Stadium (Tampa, FL) = 5M
October 5 - Sun Life Stadium (Miami, FL) = 6M
Overall, if my predictions are correct, they'll end around 297.5.
Hopefully my predictions fall short.