Barangay Calasag

Situated in San Ildefonso, Bulacan, Barangay Calasag is one of 36 barangays that make up the municipality within Central Luzon.

According to the 2020 Philippine census, Barangay Calasag had a population of 3,705. This made it the 10th largest of 36 barangays in San Ildefonso by population, placing it in the upper half of the municipality. Residents of Barangay Calasag accounted for approximately 3.20% of the total population of San Ildefonso, which stood at 115,713 in the same census year.

Between the 2015 and 2020 censuses, the population of Barangay Calasag changed from 3,578 to 3,705, a shift of +3.5% over the five-year period. This places the barangay among those with growing populations in San Ildefonso. Barangay Calasag is officially classified as urban, reflecting the density and built-up character of the area.

San Ildefonso is a municipality comprising 36 barangays, and serves as the governing unit directly responsible for local services in Barangay Calasag, including public health, sanitation, peace and order, and civil registration. Within the wider province of Bulacan, which contains 569 barangays across its component cities and municipalities, Barangay Calasag ranks 320th by 2020 population. Bulacan is classified as a 1st by the Bureau of Local Government Finance, a category that reflects the province's annual regular income.

Like every Philippine barangay, Barangay Calasag is led by an elected Punong Barangay (barangay captain) supported by seven Sangguniang Barangay members (kagawads), an SK Chairperson, a Barangay Secretary, and a Barangay Treasurer. The next Barangay and Sangguniang Kabataan Elections (BSKE) are scheduled for Monday, November 2, 2026, with officials serving four-year terms under Republic Act No. 12232.