The muscle mass estimating method acquires a height of a living body, acquires an electric resistance value measured for the living body, and uses a first variable including a height and an electric resistance value of the living body and a second variable including an electric resistance value. The muscle mass of the living body is calculated using a calculation formula including ,.筋肉量推定方法は、生体の身長を取得し、生体について測定された電気抵抗値を取得し、生体の身長及び電気抵抗値を含む第1の変数と、電気抵抗値を含む第2の変数と、を含む計算式を用いて生体の筋肉量を算出する。