Let Ω⊂RN be an open set. We consider on Ω the competitors (U,K) for the reduced Mumford–Shah functional, that is to say the Mumford–Shah functional in which the L2-norm of U term is removed, where K is a closed subset of Ω and U is a function on Ω&z.drule;K with gradient in L2. The main result of this paper is the following: there exists a constant c for which, whenever (U,K) is a quasi-minimizer for the reduced Mumford–Shah functional and B(x,r) is a ball centered on K and contained in Ω with bounded radius, the HN−1-measure of K∩B(x,r) is bounded above by crN−1 and bounded below by c−1rN−1. [Copyright &y& Elsevier]