FAO/WHO Calculator
Basal metabolic rate and energy needs by FAO/WHO
How it's calculated (FAO/WHO equations)
The FAO/WHO equations estimate basal metabolic rate by age band and sex from weight, using a linear relationship of the form BMR = a × weight(kg) + b, where a and b are specific to each age band. Total energy requirement is obtained by multiplying BMR by the physical activity level (PAL).
The approach comes from an international expert committee (1985), updated in 2001 to add weight and physical activity.
How to interpret the result
The base value is your basal metabolic rate in kcal/day. The range shown applies physical activity levels (from light to heavy), estimating the minimum and maximum daily calorie requirement for your profile.
The higher your activity level, the greater your energy requirement.
Why it matters
The FAO/WHO equations are the reference standard for estimating energy requirements at a population level and are widely used in nutrition and public health.
For a comparison with individual equations, see Harris-Benedict and Mifflin-St Jeor, or the guide to basal metabolic rate formulas.
What to enter
- Age (which sets the calculation band) and sex.
- Current weight in kg.
- Physical activity level: choose the band that reflects your real lifestyle.
What to do about your result
Use the range as a reference for planning your calorie intake based on activity.
When to see a professional: for specific needs (competitive sport, medical conditions, pregnancy, major weight loss) work with a doctor or dietitian.
Limitations of the formula
- It is designed for population estimates, not the single individual, and uses age bands.
- It does not directly account for height or body composition.
- Actual needs depend on many individual factors the equation does not capture.