How many passengers can a Boeing 747 carry?

Answer 1

Modern airliners do not have only one seating configuration.

A 747-400 with business and economy classes can hold 524 passengers.

747-400ER can hold 416 people
Passenger capacity varies by aircraft configuration (how many classes of service and seat pitch), which is determined by each airline. Some airlines have configurations in the 400-450 passenger range, while others opt for more dense configurations that can, depending on how tightly they want to pack 'em in, reach 550-600 passengers.
The most recent iteration of Boeing 747, the 400 series, is listed as carrying from 416 to 524 passengers, depending on configuration. However, I have heard of "one class" configurations in Japan that have held close to 700 passengers.
about 500, the biggest
This is the specs of the seating in the Boeing 747-200: Passengers single class: - 539. Passengers two class main deck: - 32 first class. - 388 economy class. Passengers three class main deck: - 22 first class. - 84 business class. - 131 economy class. Upper deck seating options: - 15 place lounge. - 8 first class plus 11 place lounge. - 16 first class sleeper seats. - 32 - 45 economy class.
There are 550 to 660 seats aboard a Boeing 747 not including the 10 or more other seats reserved for flight employees only.

Answer 2

A Boeing 747-400 with typical 3 class seating could carry 416 passengers. With 2 class seating it could carry 524 passengers.