We study the small and big finitistic projective, injective and flat dimensions over a non-positively graded commutative noetherian DG-ring A with bounded cohomology. Our main results generalize results of Bass and Raynaud-Gruson to this derived setting, showing that any bounded DG-module M of finite flat dimension satisfies proj dim A (M ) ≤ dim(H 0 (A))−inf(M ). We further construct DG-modules of prescribed projective dimension, and deduce that the big finitistic projective dimension satisfies the inequalities dim(HIt is further shown that this result is optimal, in the sense that there are examples that achieve either bound. As an application, new vanishing results for the derived Hochschild (co)homology of homologically smooth algebras are deduced.