Sast is a village in Ruin Rural District of the Central District of Esfarayen County, North Khorasan province, Iran. At the time of the 2006 National Census, the village's population was 2,586 in 514 households. The following census in 2011 counted 2,616 people in 641 households. The 2016 census measured the population of the village as 2,540 people …Sast is a village in Ruin Rural District of the Central District of Esfarayen County, North Khorasan province, Iran. At the time of the 2006 National Census, the village's population was 2,586 in 514 households. The following census in 2011 counted 2,616 people in 641 households. The 2016 census measured the population of the village as 2,540 people in 718 households. It was the most populous village in its rural district.