Arnia is located at . It has an average elevation of 269 metres (882 feet).
India census, Arnia had a population of 9057. Males constitute 52% of the population and females 48%. Arnia has an average literacy rate of 65%, higher than the national average of 59.5%; with 57% of the males and 43% of females literate. 12% of the population is under 6 years of age.