Problem to be solved: to provide a method of estimating a body fat quantity which is suitable for the measurement of the subject himself by himself and capable of obtaining sufficient accuracy of estimation.In the estimation method of the body fat quantity, a first length measuring step (step S403) for measuring a first length which is a length in the width direction of the front of the fuselage of the subject of the subject, and a second length measuring process (step S403) for measuring a second length which is a length in the thickness direction of the side surface of the fuselage, and a first The body fat quantity estimation process (step S404) is executed from the length and the second length to estimate the body fat contained in the fuselageDiagram【課題】日常的に被測定者自身が測定することに好適で、かつ、充分な推定の精度を得ることが可能な体脂肪量推定方法を提供する。【解決手段】体脂肪量の推定方法において、被推定者の胴体の正面の幅方向の長さである第一長さを測定する第一長さ測定工程(ステップS403)と、胴体の側面の厚さ方向の長さである第二長さを測定する第二長さ測定工程(ステップS403)と、第一長さ及び第二長さから、胴体に含まれる体脂肪量を推定する体脂肪量推定工程(ステップS404)と、を実行する【選択図】図3