WEBAbout. In 2021, Bell County, TX had a population of 365k people with a median age of 31.5 and a median household income of $57,932. Between 2020 and 2021 the population of Bell County, TX grew from 355,700 to 364,703, a 2.53% increase and its median household income grew from $54,987 to $57,932, a 5.36% increase.