Lightweight, flexible phased arrays enable new applications by dynamically changing shape during deployment and operation. However, these shape changes must be tracked and accounted for by changing the element excitation in order for the array to continue proper operation. We propose a framework for reconstructing the shape of a flexible phased array using only measurements of mutual coupling between the antennas in the array. The framework is demonstrated using a passive2.5GHzphased array and fixed to8different frames of known radii of convex and concave curvature. Our results show the ability to reconstruct shape to within ≈0.04λ position error, even incases where the phased array is bent dramatically, without any advanced knowledge or additional information. The framework is modular and can be easily adapted to other phased array systems with different antennas, frequencies, and physical constraints.