Aulos is located some 12 km south-east of Tarascon-sur-Ariège and 22 km north-west of Ax-les-Thermes. Access to the commune is by Route nationale 20 from Sinsat in the north-west passing through the north of the commune and continuing south-east to Luzenac. Access to the village is by the D522 road which branches off the N20 in the commune and goes south-east through the village continuing to Les Cabannes. A railway line passes through the commune with the nearest station at Les Cabannes. Most of the commune is heavily forested with a strip of farmland along the N20 and the D522.
The Ariège river forms the whole eastern border of the commune with no tributaries passing through the commune.
In 2010 the commune had 55 inhabitants. The evolution of the number of inhabitants is known from the population censuses conducted in the commune since 1793. From the 21st century, a census of communes with fewer than 10,000 inhabitants is held every five years, unlike larger towns that have a sample survey every year.[Note 1]
^At the beginning of the 21st century, the methods of identification have been modified by Law No. 2002-276 of 27 February 2002, the so-called "law of local democracy" and in particular Title V "census operations" allows, after a transitional period running from 2004 to 2008, the annual publication of the legal population of the different French administrative districts. For communes with a population greater than 10,000 inhabitants, a sample survey is conducted annually, the entire territory of these communes is taken into account at the end of the period of five years. The first "legal population" after 1999 under this new law came into force on 1 January 2009 and was based on the census of 2006.