What Is Resting Metabolic Rate (RMR)?
Resting Metabolic Rate (RMR) is the energy your body burns at rest to keep you alive — breathing, circulating blood, maintaining organs, and repairing cells. For most people planning nutrition, RMR is the largest single piece of daily calorie burn, often roughly 60–75% of total daily energy in sedentary adults. Fitness apps and dietitians frequently use "RMR" and "resting calories" interchangeably with closely related terms like REE and BMR.
RMR vs BMR vs REE vs TDEE
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| Term | What it means | What to focus on |
|---|---|---|
| RMR | Resting metabolic rate — energy at rest under practical conditions | Best everyday label for resting calorie planning |
| REE | Resting energy expenditure — common in clinical/research papers | Near-synonym of RMR for predictive equations |
| BMR | Basal metabolic rate — stricter fasting and rest protocols | Often ~3–10% lower than RMR when measured, not a separate formula output |
| TDEE | Total daily energy = resting × activity (TEF approximated in multiplier) | Use for maintenance, fat loss, and muscle-gain calorie targets |
This calculator shows one predictive resting estimate labeled RMR. Predictive equations cannot produce three different resting numbers for BMR, RMR, and REE — those terms describe how resting energy is measured, not three separate calculations.
Clinical/research framing: see our REE Calculator hub for the same seven equations with REE-first terminology.
How This RMR Calculator Works
Enter age, sex, weight, and usually height. Choose Auto or a specific equation. The tool estimates RMR, multiplies by your activity level for TDEE, applies your goal (maintain, lose, gain, build muscle), shows percentage-based and fixed kcal targets, and compares all seven major predictive equations when your inputs allow.
RMR is the resting base. TDEE adds daily activity. Goal calories adjust TDEE for weight change.
Predictive Equations Explained
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| Equation | Required inputs | Best suited for |
|---|---|---|
| Mifflin-St Jeor | Weight, height, age, sex | General adults (default auto) |
| Harris-Benedict (revised) | Weight, height, age, sex | Adult cross-check |
| Harris-Benedict (original) | Weight, height, age, sex | Historical comparison |
| Katch-McArdle | Weight + body fat % | Known composition |
| Cunningham | Lean body mass (kg) | Direct LBM / athletes |
| Owen | Weight + sex | Height unknown / weight-only |
| Schofield | Weight + age + sex | All ages / WHO bands |
Formula deep-dives: Mifflin, Harris-Benedict, Katch-McArdle, Cunningham, Owen, Schofield.
How Auto-Select Works
Your inputs
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| Your inputs | Auto picks | Why |
|---|---|---|
| Age under 18 | Schofield | WHO age-band lifecycle estimates |
| Lean mass entered | Cunningham | LBM-only predictor |
| Body fat % entered | Katch-McArdle | Lean mass from weight and BF% |
| Athlete, no composition, height known | Mifflin-St Jeor | Adult default + lean-mass guidance |
| Height not provided | Owen | Weight-only equation |
| Default adult + height | Mifflin-St Jeor | Frankenfield 2005 general adult preference |
How RMR Is Measured
Indirect calorimetry measures oxygen consumption and carbon dioxide production to calculate resting energy directly — the reference method in hospitals and research labs. Predictive equations (Mifflin, Harris, Katch, Cunningham, Owen, Schofield) estimate RMR from body size and composition when lab testing is unavailable. Individual error commonly reaches roughly ±10–15%.
TDEE estimate error comes from two stacked layers — and the second is usually bigger in practice.
Layer 1: BMR formula error
Mifflin-St Jeor predicts resting metabolic rate within ~10% for roughly 82% of non-obese adults and ~70% of obese adults (Frankenfield et al., 2005). That is ±150–200 kcal for many people.
Layer 2: Activity multiplier error
Picking one activity bucket too high adds ~200–400 kcal/day. Most people remember gym time but underestimate desk hours. Take our Activity Level Quiz if unsure.
Official Formulas (Reference)
Mifflin-St Jeor
Male:
BMR = (10 × kg) + (6.25 × cm)
− (5 × age) + 5
Female:
BMR = (10 × kg) + (6.25 × cm)
− (5 × age) − 161- kg
- Body weight in kilograms
- cm
- Height in centimeters
- age
- Age in years
Schofield (WHO age bands)
BMR/REE (kcal/day) = a × weight (kg) + b Coefficients (a, b) depend on sex and age band: Under 3 · 3–10 · 10–18 · 18–30 · 30–60 · 60+ years Source: Schofield (1985); FAO/WHO Table 5.2 (weight-only).
- kg, age, sex
- Weight-only kcal/day by age band
Katch-McArdle
Lean mass (kg) = weight (kg)
× (1 − body fat % / 100)
BMR = 370 + (21.6 × lean mass kg)- kg
- Body weight in kilograms
- BF%
- Body fat percentage (required)
Cunningham (1980)
RMR = 500 + (22 × lean mass kg) Lean mass can be entered directly, or: lean mass = weight (kg) × (1 − body fat % / 100)
- kg
- Lean body mass in kilograms
Worked Examples
Adult female: 28 y, 165 cm, 65 kg
Auto → Mifflin-St Jeor.
- RMR = (10 × 65) + (6.25 × 165) − (5 × 28) − 161
- RMR ≈ 1,406 kcal/day
Result: Estimated RMR ≈ 1,406 kcal/day
Adult male: 35 y, 180 cm, 80 kg
Auto → Mifflin-St Jeor.
- RMR = (10 × 80) + (6.25 × 180) − (5 × 35) + 5
- RMR ≈ 1,755 kcal/day
Result: Estimated RMR ≈ 1,755 kcal/day
Athlete: 68 kg lean mass
Lean mass entered → Cunningham.
- RMR = 500 + (22 × 68)
- RMR = 1,996 kcal/day
Result: Estimated RMR ≈ 1,996 kcal/day
TDEE from RMR
RMR 1,755 × moderately active (1.55).
- TDEE = 1,755 × 1.55
- TDEE ≈ 2,720 kcal/day maintenance
Result: Multiply RMR by activity before deficit planning
Factors Affecting RMR
RMR varies with lean mass, age, sex, genetics, hormones, sleep, stress, illness, medications, climate, and life stage. Pregnancy increases energy needs beyond standard RMR equations — this tool does not model pregnancy calories; consult your care team. Menopause and thyroid status can shift resting energy without changing weight. Equations capture population averages, not your measured metabolism.
Clinical Applications (Informational Only)
RMR estimates support hospital nutrition screening, weight-management programs, sports nutrition, diabetes care, and research — but this calculator is for personal awareness only. Clinical teams use measured RMR via indirect calorimetry, disease-specific stress factors, and professional judgment. Enable "Clinical context" in advanced options for stronger disclaimers.
Accuracy and Limitations
Frankenfield et al. (2005) found Mifflin-St Jeor within ~10% of measured RMR for roughly 82% of non-obese and ~70% of obese adults — better than many alternatives, but not exact for every individual. O'Neill et al. (2023) found several common equations, including Mifflin and Owen, differed significantly from measured RMR in pooled athlete data. Ethnic, medical, and composition factors add variation equations cannot capture.
Who Should Use This Calculator?
- Adults planning weight loss, maintenance, or muscle gain
- Athletes comparing lean-mass vs weight-based RMR estimates
- Fitness coaches and nutrition students learning predictive equations
- Older adults seeking a starting maintenance estimate (verify with trends)
- Not for: pregnancy meal planning, ICU/enteral prescribing, or replacing medical indirect calorimetry
Evidence-Based Metabolic Health Habits
No food or supplement reliably "boosts metabolism" long-term. Sustainable approaches that support healthy energy balance include resistance training to preserve lean mass during deficits, adequate protein, consistent sleep, daily movement, stress management, and hydration. Use your RMR estimate as a starting point — then let scale trends guide adjustments.
Formulas give you a starting point. Your scale trend over 2–3 weeks is the best feedback loop for finding your real maintenance calories.
- Week 1: Eat at your estimated maintenance (or goal calories) as consistently as practical. Weigh yourself daily at the same time, same conditions.
- Week 2: Calculate your weekly average weight. Compare to the prior week. Ignore day-to-day swings from sodium, hydration, or training soreness.
- Week 3: If weight is stable (±0.5 lb / ~0.2 kg), your intake is likely near maintenance. If trending up or down, adjust by 100–200 kcal/day and repeat.
Common Mistakes
- Using RMR as TDEE — multiply by activity first.
- Expecting separate BMR and REE numbers — one predictive output here.
- Fixed −500 kcal for everyone — percentage deficits scale better; fixed kcal is a rough rule of thumb.
- Guessing body fat % — weakens Katch and Cunningham accuracy.
- Overestimating activity — take the Activity Quiz if unsure.
Myths vs Facts
Myth
RMR and REE are completely different metrics.
Evidence-based view
In practice and in many papers they describe closely related resting energy. Predictive equations output one estimate.
Myth
A lower RMR means you cannot lose weight.
Evidence-based view
RMR is one input. TDEE, adherence, and NEAT matter more for outcomes.
Myth
−500 kcal/day always loses 1 lb per week.
Evidence-based view
Weight loss adapts over time. Fixed deficits are approximations; trends matter.
Myth
Athletes should ignore RMR equations.
Evidence-based view
Equations are starting points. Lean-mass formulas and trend calibration improve usefulness.
Frequently Asked Questions
Common questions about the rmr calculator.
Research & References
Each citation below supports a specific claim on this page. We explain relevance so you can verify the science yourself.
- National Academies of Sciences, Engineering, and Medicine — Factors Affecting Energy Expenditure and Requirements. Dietary Reference Intakes for Energy — NCBI Bookshelf, 2023.Defines TDEE components (REE, TEF, PAEE) and explains why population equations cannot capture individual metabolic variation.
- Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO — A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247, 1990.Primary source for the Mifflin-St Jeor BMR equation used as the default in this calculator.
- Roza AM, Shizgal HM — The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984;40(1):168-182, 1984.Source for the revised Harris-Benedict coefficients — default equation on this calculator page.
- McArdle WD, Katch FI, Katch VL — Exercise Physiology: Energy, Nutrition, and Human Performance. Lippincott Williams & Wilkins, 7th edition, 2010.Textbook reference for the lean-body-mass-based Katch-McArdle resting energy estimate.
- Frankenfield D, Roth-Yousey L, Compher C — Comparison of Predictive Equations for Resting Metabolic Rate in Healthy Nonobese and Obese Adults. J Am Diet Assoc. 2005;105(5):775-789, 2005.Meta-analysis showing Mifflin-St Jeor within ~10% of measured RMR for ~82% of non-obese and ~70% of obese adults — supports honest accuracy framing.
- O'Neill JER, Corish CA, Horner K — Accuracy of Resting Metabolic Rate Prediction Equations in Athletes: A Systematic Review with Meta-analysis. Sports Med. 2023;53(12):2373-2398, 2023.Athlete systematic review and meta-analysis — several common equations including Mifflin-St Jeor and Owen differed significantly from measured RMR in pooled athlete data; lean-mass equations (e.g., Cunningham 1980) and Ten-Haaf performed differently by population, with no single best equation for all athletes.
- Cunningham JJ — A reanalysis of the factors influencing basal metabolic rate in normal adults. Am J Clin Nutr. 1980;33(11):2372-2374, 1980.Primary source for the Cunningham equation (500 + 22 × lean body mass kg). Cunningham’s paper labels the output BMR; the 1980 reanalysis of Harris-Benedict (1919) data found LBM as the single predictor, with sex and age adding little once LBM was included.
- Schofield WN — Predicting basal metabolic rate, new standards and review of previous work. Hum Nutr Clin Nutr. 1985;39 Suppl 1:5-41, 1985.Primary source for the Schofield age- and sex-specific BMR predictive equations (weight-only kcal/day form retained in FAO/WHO Table 5.2).
- FAO/WHO/UNU — Human Energy Requirements — Report of a Joint FAO/WHO/UNU Expert Consultation. FAO Food and Nutrition Technical Report Series, 2001.Table 5.2 Schofield (1985) kcal/day coefficients by age and sex; documents retention of these equations and notes on geographic/ethnic applicability limits.
- Owen OE, Kavle EC, Owen RS, Polansky M, Caprio S, Mozzoli MA, Kendrick ZV, Bushman MC, Boden G — A reappraisal of caloric requirements in healthy women. Am J Clin Nutr. 1986;44(1):1-19, 1986.Primary source for Owen female RMR equations — non-athlete (795 + 7.18 × weight kg) and athlete (50.4 + 21.1 × weight kg) variants.
- Owen OE, Holup JL, D'Alessio DA, Craig ES, Polansky M, Smalley KJ, Kavle EC, Bushman MC, Owen LR, Mozzoli MA, Kendrick ZV, Boden G — A reappraisal of the caloric requirements of men. Am J Clin Nutr. 1987;46(6):875-885, 1987.Primary source for Owen male RMR equation (879 + 10.2 × weight kg) in men 18–82 years; found weight alone predicted RMR with age effect trivial.