The lunar surface habitat will serve as the astronauts’ “home on the moon,” providin g a pressurized facility for all crew living functions and serving as the primary location for a number of crew work functions. Adequate volume is required for each of these functions in addition to that devoted to housing the habitat systems and crew cons umables. The time constraints of the LAT -2 schedule precluded the Habitation Team from conducting a complete “bottoms -up” design of a lunar surface habitation system from which to derive true volumetric requirements. The objective of this analysis was to q uickly derive an estimated total pressurized volume and pressurized net habitable volume per crewmember for a lunar surface habitat, using a principled, methodical approach in the abs ence of a detailed design. Five “heuristic methods” were used: historica l spacecraft volu mes, human/spacecraft integration standards and design guidance , Earth -based analogs, parametric “sizing” tools, and conceptual point designs. Estimates for total pressurized volume, total habitable volume, and volume per crewmember were derived using these methods. All methods were found to provide some basis for volume estimates, but values were highly variable across a wide range, with no obvious convergence of values . Best current assumptions for required crew volume were provided as a range. Results of these analyses and future work are discussed. Earth & Space 2008