Perez is hoping to sell up to ten players before the start of the new season.
Real have already signed Ronaldo, Kaka, Raul Albiol and Karim Benzema this summer with Franck Ribery and Xabi Alonso also believed to be on Perez's wish-list.
Perez revealed: "Now we need to calm down a little, because squads usually have around 25 players and ours now has some 35.
"We need to concentrate our efforts on convincing some players that they will have to leave.
"It should not be forgotten there is a World Cup next summer and all our players want to play in it.
"If players aren't going to have the chance to participate here, they'll want to do it somewhere else, to be able to make it to the World Cup."Reuse content