In remodeling the house of an SCI (Spinal Cord injury) patient, it is necessary to accurately determine and carry out changes that are suitable with regard to the patient's ability. In our rehabilitation center, house remodeling is demonstrated for patients and family members through the use of threedimensional computer graphic images before the remodeling occurs. We have proposed an evaluation system that can show whether there is sufficient space in the remodeled house for a wheelchair to be moved or turned using a computer graphic image. The turn space is calculated using only a wheelchair size. Especially, the wheelchair turning radius determined by the physical limitation of each patient is different among SCI patients. In this study, the turning radius is calculated by measuring the moving speed of right and left wheelchair rear wheel using the rotary encoder in order to estimate the actual turn space of wheelchair for SCI patient's remodeling house.