  The critical point of a topological phase transition is described by a
conformal field theory, where finite-size corrections to energy are uniquely
related to its central charge. We investigate the finite-size scaling away from
criticality and find a scaling function, which discriminates between phases
with different topological indexes. This function appears to be universal for
all five Altland-Zirnbauer symmetry classes with non-trivial topology in one
spatial dimension. We obtain an analytic form of the scaling function and
compare it with numerical results.
