According to the 2002 census of the National Statistics Institute, San Pedro de la Paz spans an area of 112.5 km2 (43 sq mi) and has 80,447 inhabitants (38,571 men and 41,876 women). Of these, 80,159 (99.6%) lived in urban areas and 288 (0.4%) in rural areas. The population grew by 18.6% (12,630 persons) between the 1992 and 2002 censuses.
Within the electoral divisions of Chile, San Pedro de la Paz is represented in the Chamber of Deputies by José Miguel Ortiz (PDC) and Enrique Van Rysselberghe (UDI) as part of the 44th electoral district, (together with Concepción and Chiguayante). The commune is represented in the Senate by Alejandro Navarro Brain (MAS) and Hosain Sabag Castillo (PDC) as part of the 12th senatorial constituency (Biobío-Cordillera).