BMR calculator questions and answers

The site uses “BMR” because that is the familiar calculator term, but Mifflin–St Jeor and several modern validation papers concern resting energy expenditure/resting metabolic rate. True BMR requires stricter basal measurement conditions.

Mifflin–St Jeor. It is used as the primary general-adult estimate because systematic review evidence has supported it as one of the more reliable common equations in healthy adults.

There is no validated rule showing that averaging these equations produces a better individual estimate. They were derived from different populations and predictors, so the site shows them separately.

Yes. This adult calculator accepts age 18 and flags the result because Mifflin’s original derivation sample began at age 19. The equation is still a population estimate, so the study-range note stays visible.

No. This release is limited to adults age 18 and older. Pediatric and adolescent energy estimation uses different age-specific methods and growth considerations.

Yes, but the result is flagged as outside Mifflin’s original 19–78-year derivation range. Research in older adults suggests these equations can still be useful, while individual prediction error remains substantial.

Cunningham depends on fat-free mass. A body-composition equation is only as useful as the underlying body-fat or FFM measurement, so the calculator does not assume a consumer body-fat reading is automatically superior.

Athletes can differ in body composition and training status from general derivation populations. Athlete research has found the Ten Haaf equation to perform well across several athlete datasets, so it is offered as a comparison rather than a replacement for everyone.

No. Resting energy expenditure is only one component of total daily energy expenditure. Movement, structured exercise, non-exercise activity, and the thermic effect of food also contribute.

Doing that would add another uncertain estimate and turn a resting-energy calculator into a TDEE/diet tool. This project keeps those concepts separate.

No. Validation studies often score a prediction as accurate when it lands within ±10% of a measured value. That does not mean every user’s true value is guaranteed to fall within ±10% of the prediction.

Systematic reviews show meaningful individual error in overweight, obesity, and especially severe obesity. The warning is about equation uncertainty, not a diagnosis or judgment.

Low BMI can coexist with body-composition or nutritional states that are poorly represented by general equations. BMI by itself cannot diagnose malnutrition, so the site only adds an interpretation caution.

You can see a generic prediction, but it should not be used to determine pregnancy or lactation energy requirements. Physiological energy needs change across pregnancy and lactation.

A generic estimate should not drive clinical feeding decisions. Serious illness, critical care, major trauma, and burns can change expenditure, and clinical guidance may favor indirect calorimetry when feasible.

Weight loss reduces energy expenditure partly because body mass and composition change. Adaptive thermogenesis, an additional reduction beyond those changes, has also been observed in many studies, but its magnitude varies.

Research suggests a small average increase can occur in the luteal phase, but newer studies show variability and the effect can overlap normal measurement noise. This calculator does not apply a cycle-phase correction because the evidence is not precise enough for an individual adjustment.

This site does not apply a race/ethnicity multiplier. Population differences have been reported, but they are entangled with body composition, environment, sampling, and study design. A simple ethnicity correction would imply more certainty than the evidence supports.

The published equations use binary sex coefficients and were not designed to model the many body-composition and hormonal changes that can occur with gender-affirming hormone therapy. If individual precision matters, measured resting expenditure and professional interpretation are preferable.

Indirect calorimetry under standardized resting conditions measures respiratory gas exchange and is more informative than a population equation when individual precision matters.

A decimal such as 1,648.75 kcal/day looks more precise than the science allows. The calculation is performed at full precision and rounded only for display.