For human operations on the surface of Mars, methods of estimating radiation exposures from galactic cosmic rays (GCRs) are needed. To facilitate making estimates of human radiation exposures for crew operations in the Martian atmosphere, lookup tables have been generated that provide doses for critical body organs and effective doses for exposures from galactic cosmic rays anywhere on the surface of Mars. The organ doses and effective doses are tabulated for carbon dioxide atmospheric shielding areal densities ranging from 0 to 300 g cm−2 followed by aluminum spacecraft or habitat shield areal densities ranging from 0 to 100 g cm−2. The Badhwar‐O'Neill GCR model for interplanetary magnetic field potentials, ranging from the most probable solar minimum (currently 417 MV) to solar maximum conditions (1800 MV) in the solar cycle, is used as input into the calculations. This model is the standard one used for space operations at the Space Radiation Analysis Group at NASA Johnson Space Center. Use of the tables is illustrated for an environment consisting of the current galactic cosmic radiation spectrum impinging on an aluminum habitat on the surface of Mars.