The MCNPX Monte Carlo code was used to calculate energy-dependent fluence-to-effective dose conversion coefficients for neutrons, protons, electrons, photons, charged pions and muons. The FLUKA Monte Carlo code was used to calculate the spectral particle fluences of secondary cosmic rays for different altitudes, and for different combinations of solar modulation and vertical cut-off rigidity parameters. The energy-averaged fluence-to-dose conversion coefficients were obtained by folding the particle fluence spectra with the conversion coefficients for effective dose and ambient dose equivalent. They show a slight dependence on altitude, solar activity and location in the geomagnetic field.