A portable device for measuring a consumed calories includes: a respiration measurement device measuring an amount of air inhaled into a user's nose to acquire and output a respiration signal; a plurality of movement detection devices acquiring and outputting acceleration signals reflecting (or indicating) the magnitude and direction of a movement of each part of the user's body; and a controller recognizing the amount of a user's movements and movement patterns by analyzing the acceleration signal, recognizing an intensity of an exercise by analyzing the respiration signal, and calculating a consumed calories in consideration of the amount of the user's movements, the movement patterns, and the intensity of exercise. A user's consumed calories can be precisely calculated by recognizing the user's movement and even the user's respiration rate.