Abstract <p>Three calculation models are developed for estimating the cross size of a main crack formed by a blasthole in perimeter control blasting: a numerical model for calculating the equilibrium shapes and sizes of a flat crack in 2D elasticity, and two analytical models for estimating the cross size of a flat crack in two-dimensional and axially symmetric problems. The models are used to calculate the sizes of main cracks formed in granite in blasting of ammonite charges of different density. The comparison of the 3D numerical calculations with the 2D and axially symmetric modeling results has allowed finding the conditions when the analytical modeling produces such precision that makes the analytical models applicable in design of perimeter control blast patterns.</p>