Ostuncalco's 2026 population is now estimated at 20,119. In 1994, the population of Ostuncalco was 9,234. Ostuncalco experienced a decrease of -80 residents over the past year, marking an annual decline of -0.4%. These population values and projections come from CityPopulation Guatemala cities and towns census series (1994, 2002) fallback access, INE Guatemala Censo 2018 A1.2 municipio urban population and World Population Review Internal Projections .