San Carlos, CA has a population of 29,596 and is the 1,449th largest city in the United States. The population density is 5,368 per sq mi which is 2210% higher than the California average and 5825% higher than the national average. The median age in San Carlos is 43 which is approximately 19% higher than the California average of 36. In San Carlos, 65% of the population over 15 years of age are married, 78% speak English and 6% speak Spanish. 55% of San Carlos residents were born in California, 25% were born out of state, 1% were born outside of the United States and 19% were foreign born.