A method of determining a length of an object by using an electronic device includes obtaining, by the electronic device, a length, of the electronic device, between a first point and a second point on the electronic device; obtaining, by the electronic device, a tension applied to a third point on the electronic device, the third point being located between the first point and the second point; and correcting the obtained length by using the obtained tension and prestored reference tension information, the prestored reference tension information indicating a relationship of the tension applied to the third point with respect to the length of the object, and determining the corrected length as a final length of the object.