Different fractal models of porous solid are described and compared. Fractal dimension, following the different methodologies proposed to evaluate fractal dimensions, of different unweathered stones and building stones were measured using mercury porosimetry in a pore diameter range between 100 and 0.0065 mum. In all cases, fractal behaviour expands more than 1.5 orders of magnitude. In general, fractal dimension values calculated from the different models are consistent between them. Fractal dimension can be used as stone pore system descriptor and, in addition, allows the differentiation between weathered and unweathered stones.