We developed an estimation formula for resting energy expenditure (REE) in older adults with dementia according to cognitive function for use in nutrition care planning. Participants were 100 older patients with dementia (35 men and 65 women; mean age, 82.6±8.1 years and 87.0±6.2 years; body mass index (BMI), 23.1±3.5 kg/m2 and 22.6±4.0 kg/m2, respectively) who underwent REE measurement using indirect calorimetry (seated following an early morning fast) and Mini-Mental State Examination (MMSE) assessment. Based on independence in activities of daily living, MMSE score, and intelligent functions on the GBS scale, patients were divided into a mild-to-moderate dementia group (25 men, 30 women) and a severe dementia group (10 men, 35 women). The estimation formula for REE was obtained by stepwise multiple regression analysis, with the measured REE in each group as the dependent variable. We evaluated the formula’s accuracy using a Bland-Altman plot. Adjusted R-squared of the formula was 0.96 in the mild-to-moderate dementia group and 0.92 in the severe dementia group with no systematic bias, indicating in a plausible estimation formula. The severe dementia group had significantly higher sex-, age-, and body weightadjusted REE values than the mild-to-moderate dementia group, indicating possible hypermetabolism and weight loss accompanying cognitive decline.