A geometric and very general relation between the size distribution an
d the fractal dimensions of a set of objects is presented. The applica
tions are numerous, ranging from fragmentation experiments to time ser
ies. For example, it may be used to understand the fragment-size distr
ibution of fragmenting gypsum. The formalism also generalizes to self-
affine fractals, and here it is applied to the scaling properties of s
elf-interactions in (1+1)-d directed percolation.