About 29,000 seats will go to the British public for the 100m final, London 2012 chief executive Paul Deighton said today.
This is around only 50 per cent of the 58,000-59,000 capacity which will be left in the Olympic Stadium after space needed for big screens, the press and camera positions are taken out.
Tickets to accredited officials and executives from sports federations, international spectators and athletes plus seats with obstructed views also cut down the tickets available at the showpiece 100m final at the 80,000-seater Olympic Stadium .
Deighton said: "On the narrowest definition, 50% of the tickets for the 100m final will be distributed through the broad approach to selling tickets to the UK public."
There are two huge spaces for big screens at each end of the Olympic Stadium, which immediately cuts the capacity by 4,500 to 75,500.
Another 17,000 seats are taken out of the equation through a mix of accredited media, sports representatives, athletes and because the views are obstructed.
This 17,000 includes 10,000 which are for the media, including both broadcast and press reporters.
Mr Deighton told the London Assembly: "There are over 20,000 accredited media who come to the Games.
"You will appreciate the majority of the world - billions of people as opposed to the small number in the stadium - consume the Games through the media. We have to make provision for TV and press.
"They take 10,000 spaces. It is absolutely standard practice."
The 17,000 also includes 2,000 seats for athletes.
"It is part of the Games that you make a provision for the athletes to come and watch the sport," Mr Deighton said.
"It is all part of the deal. It happens at every Games and it happens at every venue."
Another 2,000 seats are for accredited people such as the International Olympic Committee and the international sports federations.
Estimates suggest there will also be approximately 3,000 seats with obstructed views, largely as a result of press and camera positions, he claimed.
Deighton continued: "We will not sell a seat if we think it obstructed but we will not know whether it is fully obstructed until the cameras are all in position."
This reduces capacity to an estimate of just under 60,000 seats.
Deighton noted: "Our commitment is to sell 75% of Olympic tickets to the public with the remaining 25% going to client groups (such as international spectators, sponsors and hospitality partners).
"For the prime events those numbers are different and it may be as low as 30% or 40% going through the public ticketing process.
"Of the approximately 60,000 seats available, about half have been sold to those client groups, such as international public.
"Anyone who has been watching this process will have noticed how extremely efficient the British public have been at getting the tickets that have been on sale in Europe.
"It is hard to track that but in practice a very significant number of the European allocation has ended up in British hands because we are very efficient in buying tickets off the internet."
He also said that sponsors share out about half of their tickets to the public via competitions or as a reward to their workers.
Deighton argued that "a reasonable person would say that half of their tickets are actually going to the public".
He added: "Of the remaining tickets, we have sold just over 20,000 to the UK public and the remaining tickets that we will release will be sold to the public in the sale at the end of April.
"When we finalise which seats are obstructed, those seats will get dribbled out through to July."
Without adding in tickets gained from sponsors or internationally, he concluded: "On the narrowest definition, 50% of the tickets for the 100m final will be distributed through the broad approach to the selling tickets to the UK public."