At the time of the 2006 National Census, Qahan's population was 715 in 193 households, when it was a village in Qahan Rural District of Khalajestan District, Qom County.[6] The following census in 2011 counted 747 people in 255 households.[7] The 2016 census measured the population of the village as 784 people in 286 households. It was the most populous village in its rural district.[2]
After the census, the rural district was separated from the county in the establishment of Jafarabad County and transferred to the new Qahan District.[4] Qahan was elevated to the status of a city in May 2023.[8]
^Qahan can be found at GEOnet Names Server, at this link, by opening the Advanced Search box, entering "-3078760" in the "Unique Feature Id" form, and clicking on "Search Database".