Résumé : A coxometric evaluation is helpful for the diagnosis and the prognosis of hip dysplasia. These measurements also give an intrinsic guide to the surgeon for total hip arthroplasty. A coxometric protractor is drawn on the majority of the goniometers and allows the measurement of the angle of internal and external roof, the angle of the acetabular roof obliquity and the femoral neck-shaft angle on a hip AP XRay. The purpose of this report is to demonstrate that on the same X Ray, the adequate placement of the coxometric protractor allows to calculate the inclination angle, the acetabular anteversion angles and the anterior roof angle.