Balsac is located some 10 km north-west of Rodez and 8 km south-east of Saint-Christophe-Vallon, immediately west of Rodez–Marcillac Airport. Access to the commune is by the D598 which branches off the D57 west of the commune and passes through the village continuing to join the D840 south-east of the commune. The D626 goes north-east from the village to join the D840. The commune is entirely farmland.
The Ruisseau des Parranies and its tributary the Ruisseau du Sauvage rise in the south of the commune and flow west then north-west, forming part of the western border of the commune, to join the Ruisseau de l'Ady west of the commune.
In 2010 the commune had 611 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 communes that have a sample survey every year.[Note 1]
Christian-Pierre Bedel, preface by José Monestier, Marcilhac, Balsac, Claravals, Moret, Muret, Nòuviala, Prunas, Salas-Comtals, Sent-Cristòfa, Valadin / Christian-Pierre Bedel e los estatjants del canton de Marcilhac, Rodez, Mission départementale de la culture, 2001, Al canton collection, 392 pages, ill., cov. ill.; 28 cm, ISBN 2-907279-52-1, ISSN 1151-8375, BnF 38803935q (French)
^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 in 1 January 2009 and was based on the census of 2006.