Sanibel, FL has a population of 7,044 and is the 5,157th largest city in the United States. The population density is 437 per sq mi which is 49% higher than the Florida average and 383% higher than the national average. The median age in Sanibel is 66 which is approximately 58% higher than the Florida average of 42. In Sanibel, 79% of the population over 15 years of age are married, 93% speak English and 2% speak Spanish. 10% of Sanibel residents were born in Florida, 79% were born out of state, 1% were born outside of the United States and 9% were foreign born.