According to the 2021 census gazetteer files, Milks Grove Township has a total area of 36.35 square miles (94.15 km2), all land.

As of the 2020 census[1] there were 204 people, 100 households, and 100 families residing in the township.

There were 75 housing units at an average density of 2.06 per square mile (0.80/km2).

The racial makeup of the township was 87.75% White, 0.00% African American, 0.49% Native American, 0.00% Asian, 0.00% Pacific Islander, 0.49% from other races, and 11.27% from two or more races.

There were 100 households, out of which 53.00% had children under the age of 18 living with them, 59.00% were married couples living together, 0.00% had a female householder with no spouse present, and 0.00% were non-families.