B Background: Orthodontic treatment is applied to obtain a good occlusion. Ideal treatment begins with correct diagnosis, one way to get a diagnosis and determine a plan of orthodontic treatment is the measurement of space analysis. Space analysis is measurement the amount of space available on the dental arch and the amount of space needed for the canines, first premolars, and second premolars which will erupt. The measurement of space analysis is required during the period of mixed dentition. Moyers analysis and Tanaka-Johnston analysis which are frequently used. Objective: To determine differences in the prediction of the mesiodistal width of the canines, first premolars, and second premolars using Moyers analysis and Tanaka-Johnston analysis with the actual tooth size. Methods: Measurements space analysis carried out by measuring the dental cast of orthodontic patients (6-12 years old) using a digital calipers. The measurement of mesiodistal width prediction of canines, first premolars, and second premolars is applied to the four permanent incisor of the mandible which had erupted perfect for space analysis methods to performed. The number of all four mandible incisors matched with Moyers 75% probability tables while for the Tanaka- Johnston analysis using the half formula of the four incisor teeth of the mandible, add 11.0mm for the maxilla, and add 10.5mm for the mandible. Results: The prediction of mesiodistal width of the canines, first premolars, and second premolars in maxilla and mandible by using Moyers analysis methods and Tanaka-Johnston analysis exceeds the real tooth size that has been measured in this study. Conclusion: The measurement of space analysis is better conducted using Tanaka-Johnston analysis method as it produced the most accurate result of the real tooth size.