Belmont, CA has a population of 26,918 and is the 1,605th largest city in the United States. The population density is 5,809 per sq mi which is 2400% higher than the California average and 6312% higher than the national average. The median age in Belmont is 40 which is approximately 11% higher than the California average of 36. In Belmont, 64% of the population over 15 years of age are married, 62% speak English and 8% speak Spanish. 48% of Belmont residents were born in California, 19% were born out of state, 2% were born outside of the United States and 31% were foreign born.