Calorie estimation, activity multipliers and macro planning
Estimate adult resting energy with the Mifflin–St Jeor equation, apply a selected activity multiplier and planning adjustment, and convert calorie percentages into protein, carbohydrate and fat grams.
This page provides an equation-based estimate for education and planning. It does not diagnose a condition, measure an individual response, or replace professional care.
How to use this health calculator
- Choose appropriate inputs: Enter measurements using the units and ranges shown.
- Review the assumptions: Confirm that the model applies before interpreting the result.
- Calculate and interpret: Read the result together with its limitations and cautions.
- Use professional guidance when needed: Do not use a general calculator to change medication, treatment, or a clinician-directed plan.
Formula and variables
The Mifflin–St Jeor equation estimates resting energy from weight, height, age and the equation’s sex-coded constant. Activity and goal factors are planning assumptions, not measured expenditure.
RMR = 10W + 6.25H − 5A + sex-coded constant; target = RMR × activity × goal adjustment- W — Weight
- Body weight in kilograms.
- H — Height
- Height in centimeters.
- A — Age
- Adult age in years.
Worked example: maintenance estimate
A 35-year-old woman weighs 70 kg, is 170 cm tall and selects a 1.375 activity multiplier.
- Age
- 35 years
- Weight
- 70 kg
- Height
- 170 cm
- Activity
- 1.375
- RMR = 10×70 + 6.25×170 − 5×35 − 161 = 1,426.5 kcal/day.
- Maintenance estimate = 1,426.5 × 1.375 = 1,961 kcal/day.
Result: The maintenance starting estimate is about 1,961 kcal/day before any selected planning adjustment.
Actual expenditure can differ materially; use trends over time and qualified guidance rather than treating the estimate as a measured requirement.
Understanding your results
Equation result
The numerical output follows the displayed formula and entered assumptions.
Personal interpretation
Individual biology, measurement error, environment, health conditions and medicines can change real-world outcomes.
Assumptions
- The user is an adult within the validated input ranges.
- The activity multiplier reasonably represents average activity.
- Macro percentages total 100%.
Limitations
- The equation does not measure metabolism or total expenditure.
- Activity multipliers can substantially misestimate individual needs.
- Pregnancy, breastfeeding, adolescence, eating disorders and therapeutic diets are outside scope.
Common mistakes
- Treating maintenance calories as exact.
- Selecting an activity multiplier from aspiration rather than typical activity.
- Changing intake aggressively from a single estimate.
- Entering macro percentages that do not total 100%.
Practical use cases
Educational estimate
Explore how the inputs affect the equation result.
Consistent tracking
Compare estimates only when methods, units and conditions are consistent.
Planning and decision guide
Treat cautions as part of the result
The ±10% goal option is a modest planning scenario, not a clinical prescription.
People with medical or nutritional risk should use individualized advice from a qualified clinician or registered dietitian.
Escalate symptoms or clinical questions
Seek qualified medical advice for symptoms, diagnosed conditions, medicines, pregnancy, or individualized treatment decisions.
Frequently asked questions
Does this measure my metabolism?
No. It applies a population prediction equation.
Why can actual maintenance differ?
Movement, body composition, adaptation, measurement error and individual biology affect expenditure.
Are the macro grams mandatory targets?
No. They are arithmetic conversions of the percentages you selected.
Sources and review
- A new predictive equation for resting energy expenditure in healthy individuals — American Journal of Clinical Nutrition (PubMed). Accessed 2026-08-03.
- Dietary Guidelines for Americans — U.S. Departments of Agriculture and Health and Human Services. Accessed 2026-08-03.
Reviewed 2026-08-03.