Jhajjar is located at . It has an average elevation of 220 metres (721 feet).
India census, Jhajjar had a population of 39,004. Males constitute 54% of the population and females 46%. Jhajjar has an average literacy rate of 69%, higher than the national average of 59.5%: male literacy is 76%, and female literacy is 61%. In Jhajjar, 14% of the population is under 6 years of age.