The most important factor affecting the surgical outcome and clinical success in spinal deformity surgery is preoperative planning. Clinical recording and radiological evaluations enable decision-making and, most importantly, managing the surgical process. Radiological measurements are the basis of preoperative evaluations. Measurements are used in all stages of defining the existing deformity, identifying the problem and solution, and evaluating the result. In this review, basic concepts and how to make measurements are explained on radiological images and illustrations.