Wire electrical discharge turning (WEDT) process is one of the emerging non-traditional machining processes for manufacture of micro- and axi-symmetric components. In WEDT process, material is removed by successive sparks that form craters. The material removal by crater formation is associated with energy supplied in the gap referred as discharge energy. This energy must be controlled for effective machining. In this paper, a model is proposed for predicting the crater diameter based on anode erosion. Finite element method (FEM) is used to simulate the crater for different plasma flushing efficiency. Effect of discharge energy developed in the gap, physio-thermal properties of the material are considered for modeling. The erosion energy required to form a crater is also evaluated using anode erosion model. The proposed models are validated by conducting WEDT experiments on high-tensile steel [AISI 4340]. The crater morphology is investigated by using images obtained from scanning electron microscope (SEM) and energy-dispersive X-ray analysis. The crater diameter predicted by anode erosion and FEM models are compared with diameter obtained from SEM micrograph. The results obtained from the proposed models are well in agreement with the experimental results. The anode erosion model predicts the crater diameter and erosion energy with an average absolute error of 5.65 and 17.86 %, respectively. By estimating the energy required to erode a material and by setting appropriate process settings, the discharge energy can be effectively utilized for material removal. © 2014, Springer-Verlag London.