The Atlas V vehicle, developed under the US Air Force EELV contract, builds upon the improvements made for the Atlas III.   In addition to the NPO Energomash RD-180 first stage engine, the Atlas V incorporates a reinforced first stage structure as well as increased first stage propellant load.  These modifications, combined with the stretched Atlas IIIB Centaur upper stage, allow the Atlas V to place more than 10,000 lb into a geosynchronous transfer orbit.  The Heavy variant of the Atlas V, which uses three common core bosters, can place over 13,000 lb directly into a geostationary orbit.  This configuration, however, is not currently being marketed commercially.

Lockheed Martin has proposed variants of the Atlas V which incorporate different arrangements of solid strap-on boosters to increase the payload performance of the single common core variant up to 18,000 lb to GTO.  To differentiate the different Atlas V configurations, Lockheed Martin devised a secondary numbering system.  The first number identifies the fairing diameter in meters (3, 4 or 5 meter fairing).  The second number identifies the number of solid strap-on boosters (0 through 5).  The final number identifies the number of second stage RL-10 engines (either 1 or 2).  As an example, an Atlas 5 532 has a five meter fairing, three solid strap-on boosters, and two second stage RL-10 engines.  According to the ILS Payload Planner's Guide, a single engine RL-10 second stage is used for high altitude (MEO and GTO) missions while the two engine variant is used for LEO missions.