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Calculating BMR

Basal Metabolic Rate (BMR) and Resting Metabolic Rate (RMR) are measures of resting energy expenditure, representing the minimum amount of energy required to sustain the body's vital functions, including the heart, lungs and temperature regulation.

The BMR can account for about 60-70% of the body's daily energy consumption. BMR goes to supporting the ongoing metabolic work of the body's cells, such activities as pumping blood around the body, digesting food, respiration, maintaining body temperature and for cells to grow.

Described here are a couple of methods for estimating BMR - see also information about the direct measure of BMR and RMR. By multiplying BMR by an activity factor, you can estimate how many calories are required each day to maintain body weight based on your daily activity level.

Harris-Benedict Equation for Calculating BMR

The Harris-Benedict Equation (Harris & Benedict, 1919) has for a long time been the standard formula and is widely used for estimating BMR. The Harris-Benedict equation was first published in 1919. Since then there have been many other studies attempting to improve it, with limited success.

Metric Units

Imperial Units

Mifflin-St Jeor Equation for Calculating BMR

For men: BMR (kcal / day) = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5

For women: BMR (kcal / day) = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161

Mifflin Equation for Calculating BMR

Another commonly used equation for calculating RMR is the Mifflin equation. Use the calculations below to calculate BMR, where: Wt = weight in kg, Ht = height in cm, A = age in years.

men: kcal/day = (13.75 x Wt) + (5 x Ht) - (6.76 x Age) + 66
women: kcal/day = (9.56 x Wt) + (1.85 x Ht) - (4.68 x Age) + 655

Schofield Equation for Calculating BMR

Use the table below to find the equation for estimating BMR for the appropriate age and sex category, using weight in kilograms (Warwick, 1989).


Age (years) Equation for BMR (MJ/day)
10-18 (0.074 x weight) + 2.754
18-30 (0.063 x weight) + 2.896
30-60 (0.048 x weight) + 3.653
> 60 (0.049 x weight) + 2.459


Age (years) Equation for BMR (MJ/day)
10-18 (0.056 x weight) + 2.898
18-30 (0.062 x weight) + 2.036
30-60 (0.034 x weight) + 3.538
> 60 (0.038 x weight) + 2.755


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