A distance measurement method for a single-camera condition is proposed. The aim is to implement a way to find the distance of an object in front of the imaging system in indoor environment. In this method, the first step is to extract the appropriate vertical floor line from the snapshots sequence. Moreover, the line passing through the base side of the object is found simultaneously with the floor line. Then, the part of the floor line starting from this point is measured in pixels, by taking the intersection point of these lines, and converted to distance between the camera and the object. The proposed method is applicable for flat indoor buildings with regular lines on the floor, while many buildings are in such a situation. Experimental results are carried out by using MATLAB to estimate the measured distance by the proposed method.