Understand this tool
What a BMR estimate means
- What the concept means
- Basal metabolic rate (BMR) is the energy the body expends to sustain essential functions under tightly controlled resting conditions.
- Why it exists
- Predictive equations estimate that expenditure from variables such as age, sex, height, and weight when laboratory measurement is unavailable.
- When to use it
- Use it as a population-based energy estimate and a starting point for understanding total expenditure.
- What the result means—and does not mean
- The number is not directly measured metabolism and can differ from an individual’s true expenditure because body composition, health, medication, temperature, and measurement conditions matter.
How the equations developed
Harris and Benedict published early twentieth-century equations derived from measured subjects. Later datasets led to revisions and alternatives, including the 1990 Mifflin–St Jeor equation used by this page.
BMR, resting metabolic rate (RMR), and total daily energy expenditure (TDEE) are related but not identical. RMR is measured under less restrictive resting conditions; TDEE adds activity and other energy costs.
Key concepts
Key concepts
- Basal metabolic rate
- Energy used under standardized basal conditions.
- Resting metabolic rate
- Resting expenditure measured under less restrictive conditions.
- Total daily energy expenditure
- All energy expended across a day.
- Harris–Benedict equation
- An early family of predictive metabolic equations.
- Mifflin–St Jeor equation
- A 1990 predictive equation for resting energy expenditure.
Method or process
Calculation method
How the equations developed
Harris and Benedict published early twentieth-century equations derived from measured subjects. Later datasets led to revisions and alternatives, including the 1990 Mifflin–St Jeor equation used by this page.
BMR, resting metabolic rate (RMR), and total daily energy expenditure (TDEE) are related but not identical. RMR is measured under less restrictive resting conditions; TDEE adds activity and other energy costs.
Formula or rule
Mifflin–St Jeor = 10w + 6.25h − 5a + sex-specific constantCompare the concepts
BMR, RMR, and TDEE
| Measure | Scope | Typical relation |
|---|---|---|
| BMR | Strict basal conditions | Core physiological energy |
| RMR | Resting conditions | Often slightly broader |
| TDEE | Whole day | Resting energy plus activity and other costs |
Common mistakes
Common mistakes
- Reading a prediction as a measurement.
- Using BMR as the amount necessarily eaten.
- Ignoring uncertainty and individual context.
Edge cases and limits
Edge cases and limits
- Pregnancy, illness, growth, or unusual body composition can reduce equation fit.
- Sex categories in legacy equations do not represent every physiology.