St. Petersburg, FL has a population of 253,585 and is the 78th largest city in the United States. The population density is 4,105 per sq mi which is 1298% higher than the Florida average and 4431% higher than the national average. The median age in St. Petersburg is 42 which is approximately 2% higher than the Florida average of 42. In St. Petersburg, 47% of the population over 15 years of age are married, 88% speak English and 5% speak Spanish. 41% of St. Petersburg residents were born in Florida, 47% were born out of state, 2% were born outside of the United States and 10% were foreign born.