A biometric information processing device includes a heart rate detection unit, a relative heart rate calculation unit, a relative oxygen intake calculation unit, an oxygen intake estimation unit and a calorie expenditure calculation unit. The relative heart rate calculation unit calculates a relative heart rate obtained from a first difference over a second difference, the first difference being by subtracting a resting heart rate of the subject from the heart rate, the second difference being by subtracting the resting heart rate from a maximum heart rate. The relative oxygen intake calculation unit calculates a relative oxygen intake based on the relative heart rate. The oxygen intake estimation unit estimates the oxygen intake from the relative oxygen intake. The calorie expenditure calculation unit calculates calorie expenditure based on the oxygen intake.
