2020 census

The 2020 United States census counted 260 people, 129 households, and 68 families in Grinnell.^[7][8] The population density was 528.5 per square mile (204.0/km²). There were 151 housing units at an average density of 306.9 per square mile (118.5/km²).^[8][9] The racial makeup was 94.62% (246) white or European American (92.69% non-Hispanic white), 0.0% (0) black or African-American, 0.0% (0) Native American or Alaska Native, 0.0% (0) Asian, 0.0% (0) Pacific Islander or Native Hawaiian, 2.31% (6) from other races, and 3.08% (8) from two or more races.^[10] Hispanic or Latino of any race was 5.38% (14) of the population.^[11]

Of the 129 households, 16.3% had children under the age of 18; 41.9% were married couples living together; 24.8% had a female householder with no spouse or partner present. 44.2% of households consisted of individuals and 23.3% had someone living alone who was 65 years of age or older.^[8] The average household size was 2.0 and the average family size was 2.8.^[12] The percent of those with a bachelor’s degree or higher was estimated to be 16.2% of the population.^[13]

21.5% of the population was under the age of 18, 6.2% from 18 to 24, 20.0% from 25 to 44, 23.8% from 45 to 64, and 28.5% who were 65 years of age or older. The median age was 46.0 years. For every 100 females, there were 83.1 males.^[8] For every 100 females ages 18 and older, there were 90.7 males.^[8]

The 2016-2020 5-year American Community Survey estimates show that the median household income was $55,769 (with a margin of error of +/- $9,039) and the median family income was $62,500 (+/- $5,637).^[14] Males had a median income of $60,368 (+/- $11,714) versus $24,583 (+/- $12,636) for females. The median income for those above 16 years old was $41,667 (+/- $9,898).^[15] Approximately, 1.4% of families and 2.6% of the population were below the poverty line, including 3.2% of those under the age of 18 and 5.3% of those ages 65 or over.^[16][17]

2010 census

As of the census^[18] of 2010, there were 259 people, 135 households, and 81 families residing in the city. The population density was 507.8 inhabitants per square mile (196.1/km²). There were 156 housing units at an average density of 305.9 per square mile (118.1/km²). The racial makeup of the city was 100.0% White. Hispanic or Latino of any race were 0.4% of the population.

There were 135 households, of which 14.1% had children under the age of 18 living with them, 54.8% were married couples living together, 3.7% had a female householder with no husband present, 1.5% had a male householder with no wife present, and 40.0% were non-families. 38.5% of all households were made up of individuals, and 18.6% had someone living alone who was 65 years of age or older. The average household size was 1.92 and the average family size was 2.48.

The median age in the city was 55.9 years. 13.5% of residents were under the age of 18; 5% were between the ages of 18 and 24; 16.6% were from 25 to 44; 32.8% were from 45 to 64; and 32% were 65 years of age or older. The gender makeup of the city was 52.1% male and 47.9% female.

2000 census

As of the census^[19] of 2000, there were 329 people, 149 households, and 87 families residing in the city. The population density was 662.2 inhabitants per square mile (255.7/km²). There were 158 housing units at an average density of 318.0 per square mile (122.8/km²). The racial makeup of the city was 99.70% White and 0.30% African American. Hispanic or Latino of any race were 0.61% of the population.

There were 149 households, out of which 19.5% had children under the age of 18 living with them, 51.7% were married couples living together, 4.0% had a female householder with no husband present, and 41.6% were non-families. 39.6% of all households were made up of individuals, and 28.2% had someone living alone who was 65 years of age or older. The average household size was 2.21 and the average family size was 2.98.

In the city, the population was spread out, with 22.5% under the age of 18, 7.6% from 18 to 24, 19.5% from 25 to 44, 21.6% from 45 to 64, and 28.9% who were 65 years of age or older. The median age was 45 years. For every 100 females, there were 104.3 males. For every 100 females age 18 and over, there were 105.6 males.

The median income for a household in the city was $35,833, and the median income for a family was $41,750. Males had a median income of $27,167 versus $21,500 for females. The per capita income for the city was $20,056. About 9.2% of families and 8.2% of the population were below the poverty line, including 8.5% of those under age 18 and 8.6% of those age 65 or over.