Orinda, CA has a population of 18,936 and is the 2,308th largest city in the United States. The population density is 1,473 per sq mi which is 534% higher than the California average and 1526% higher than the national average. The median age in Orinda is 48 which is approximately 34% higher than the California average of 36. In Orinda, 75% of the population over 15 years of age are married, 83% speak English and 2% speak Spanish. 53% of Orinda residents were born in California, 29% were born out of state, 2% were born outside of the United States and 16% were foreign born.