At the time of the 2006 National Census, the village's population was 1,114 in 292 households, when it was in Darjazin-e Olya Rural District[b] of the former Qorveh-ye Darjazin District of Razan County.[5] The following census in 2011 counted 1,133 people in 342 households.[6] The 2016 census measured the population of the village as 1,053 people in 334 households.[2]
After the census, the district was separated from the county in the establishment of Dargazin County. The rural district was transferred to the new Shahanjarin District and renamed Dargazin-e Olya Rural District. Kaj was transferred to Dargazin-e Sharqi Rural District created in the district.[4]
^Kaj can be found at GEOnet Names Server, at this link, by opening the Advanced Search box, entering "-3068622" in the "Unique Feature Id" form, and clicking on "Search Database".