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

Term

RMR

What it means

Resting metabolic rate — energy at rest under practical conditions

What to focus on

Best everyday label for resting calorie planning

Term

REE

What it means

Resting energy expenditure — common in clinical/research papers

What to focus on

Near-synonym of RMR for predictive equations

Term

BMR

What it means

Basal metabolic rate — stricter fasting and rest protocols

What to focus on

Often ~3–10% lower than RMR when measured, not a separate formula output

Term

TDEE

What it means

Total daily energy = resting × activity (TEF approximated in multiplier)

What to focus on

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. Basal energy / Harris-BEE framing: see our BEE Calculator.

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 to TDEE energy flowRMRat rest× Activity1.2–1.9TDEEmaintenanceGoal adjust% or fixed kcal

RMR is the resting base. TDEE adds daily activity. Goal calories adjust TDEE for weight change.

Predictive Equations Explained

Equation

Mifflin-St Jeor

Required inputs

Weight, height, age, sex

Best suited for

General adults (default auto)

Equation

Harris-Benedict (revised)

Required inputs

Weight, height, age, sex

Best suited for

Adult cross-check

Equation

Harris-Benedict (original)

Required inputs

Weight, height, age, sex

Best suited for

Historical comparison

Equation

Katch-McArdle

Required inputs

Weight + body fat %

Best suited for

Known composition

Equation

Cunningham

Required inputs

Lean body mass (kg)

Best suited for

Direct LBM / athletes

Equation

Owen

Required inputs

Weight + sex

Best suited for

Height unknown / weight-only

Equation

Schofield

Required inputs

Weight + age + sex

Best suited for

All ages / WHO bands

Formula deep-dives: Mifflin, Harris-Benedict, Katch-McArdle, Cunningham, Fat-Free Mass, Lean Body Mass, Owen, Schofield.

How Auto-Select Works

Your inputs

Age under 18

Auto picks

Schofield

Why

WHO age-band lifecycle estimates

Your inputs

Lean mass entered

Auto picks

Cunningham

Why

LBM-only predictor

Your inputs

Body fat % entered

Auto picks

Katch-McArdle

Why

Lean mass from weight and BF%

Your inputs

Athlete, no composition, height known

Auto picks

Mifflin-St Jeor

Why

Adult default + lean-mass guidance

Your inputs

Height not provided

Auto picks

Owen

Why

Weight-only equation

Your inputs

Default adult + height

Auto picks

Mifflin-St Jeor

Why

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.

  1. RMR = (10 × 65) + (6.25 × 165) − (5 × 28) − 161
  2. RMR ≈ 1,406 kcal/day

Result: Estimated RMR ≈ 1,406 kcal/day

Adult male: 35 y, 180 cm, 80 kg

Auto → Mifflin-St Jeor.

  1. RMR = (10 × 80) + (6.25 × 180) − (5 × 35) + 5
  2. RMR ≈ 1,755 kcal/day

Result: Estimated RMR ≈ 1,755 kcal/day

Athlete: 68 kg lean mass

Lean mass entered → Cunningham.

  1. RMR = 500 + (22 × 68)
  2. RMR = 1,996 kcal/day

Result: Estimated RMR ≈ 1,996 kcal/day

TDEE from RMR

RMR 1,755 × moderately active (1.55).

  1. TDEE = 1,755 × 1.55
  2. 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.

  1. Week 1: Eat at your estimated maintenance (or goal calories) as consistently as practical. Weigh yourself daily at the same time, same conditions.
  2. Week 2: Calculate your weekly average weight. Compare to the prior week. Ignore day-to-day swings from sodium, hydration, or training soreness.
  3. 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.

Suggested next steps

Metabolic Age Calculator

Mifflin age-equivalence + composition

BEE Calculator

Classic Harris BEE + clinical terminology

Fat-Free Mass Calculator

FFM from DEXA, Navy & manual BF%

Lean Body Mass Calculator

Boer, James, Hume when BF% unknown

Calorie Surplus Calculator

Bulking twin — surplus presets & weekly gain

REE Calculator

Same 7 equations, REE-first terminology

BMR Calculator

Simpler 3-formula compare

Macro Calculator

Full protein, fat, carb split

Maintenance Calculator

Verify maintenance from trends

Frequently Asked Questions

Common questions about the rmr calculator.

What is Resting Metabolic Rate (RMR)?
RMR is the energy your body burns at rest to maintain vital functions — breathing, circulation, organ work, and cell repair. It is closely related to Resting Energy Expenditure (REE) and Basal Metabolic Rate (BMR), which differ mainly in how strictly they are measured in a lab.
Is RMR the same as REE?
In practice, yes for most calorie planning. REE is common in clinical papers; RMR is common in fitness and dietetics. Predictive equations output one resting estimate — not two separate numbers.
Is RMR the same as BMR?
They describe closely related concepts. BMR uses stricter measurement conditions (fasting, thermoneutral rest). RMR is measured under less strict conditions and is often a few percent higher. This calculator shows one predictive estimate labeled RMR.
How do I calculate my RMR online?
Enter age, sex, weight, and usually height in this calculator. Choose Auto or a specific equation. The tool estimates RMR, converts to TDEE with your activity level, and shows goal calories and formula comparisons.
Which RMR equation is most accurate?
No single equation fits everyone. Frankenfield (2005) often favors Mifflin-St Jeor for general adults when height is known. Athletes may compare lean-mass equations (O'Neill 2023). Schofield fits pediatric age bands. Compare formulas and calibrate with weight trends.
What does Auto (recommended) select?
Rules apply in priority order: under 18 → Schofield; direct lean mass → Cunningham; body fat % → Katch-McArdle; athlete without composition (height known) → Mifflin; no height → Owen; default adult with height → Mifflin-St Jeor.
How does the RMR calculator work?
It estimates resting metabolic rate from validated predictive equations, multiplies by an activity factor for TDEE, applies your goal (maintain, lose, gain, build muscle), shows percentage and fixed kcal targets, macro preview, and compares all seven equations when inputs allow.
Why do different RMR calculators give different results?
Different equations, activity multipliers, and rounding change outputs. Even the same equation differs if height, age, or body composition inputs differ. Use 2–3 weeks of weight trends to judge which estimate fits you.
What is indirect calorimetry?
The reference lab method measuring oxygen consumption and carbon dioxide production to calculate resting energy directly. Predictive RMR equations are practical estimates — not replacements for measurement.
How much does RMR testing cost?
Indirect calorimetry at a clinic or sports lab often costs roughly $75–$250+ depending on location and provider. Predictive calculators are free starting estimates when lab testing is not needed or available.
Can I use RMR for weight loss?
Yes — as a starting point. Multiply RMR by activity to get TDEE, then eat below TDEE for fat loss. Percentage deficits scale better than fixed kcal for different body sizes; calibrate from weight trends.
Does RMR equal TDEE?
No. TDEE = RMR × activity factor (thermic effect of food is approximated in the multiplier). RMR is only the resting component — multiply by activity before planning deficits or surpluses.
What are fixed kcal targets (−250, −500, −750)?
Rough rule-of-thumb deficits from your TDEE. −500 kcal/day is often cited as ~1 lb/week fat loss, but real results vary. Percentage goals (−10/−15/−20%) scale better; fixed kcal targets are supplementary approximations.
Should I use fixed kcal or percentage deficits?
Percentage deficits (shown in the goal grid) scale with your TDEE and suit most people. Fixed kcal targets are familiar shortcuts — use either as a starting point and adjust from scale trends.
What macro split does the RMR calculator suggest?
A macro preview based on your goal calories and a preset (balanced or higher-protein for fat loss/build muscle). Use the Macro Calculator for full customization, meal splits, and carb cycling.
Can athletes rely on predictive RMR equations?
With caution. O'Neill et al. (2023) found several common equations, including Mifflin and Owen, differed significantly from measured RMR in pooled athlete data. Lean-mass equations may fit better when body composition is known.
Can I use this RMR calculator during pregnancy?
Standard RMR equations do not model pregnancy energy needs. Enable pregnancy mode for disclaimers only — consult your obstetric care team or dietitian for individualized guidance. Deficits and surpluses are blocked in pregnancy mode.
Is this calculator suitable for clinical use?
No. It provides population-based estimates for personal awareness only. Clinical teams use measured RMR via indirect calorimetry and professional judgment — not a web calculator for ICU or enteral prescribing.
Can children use this RMR calculator?
Auto-select uses Schofield for users under 18. Pediatric meal planning requires professional guidance — this tool is educational only.
Why show a ±10% range?
Population equations commonly miss measured RMR by roughly 10–15%. The range sets realistic expectations before you calibrate with real weight data.
What activity multipliers does this use?
Fitness-oriented multipliers from 1.2 (sedentary) to 1.9 (extra active). WHO/clinical PAL categories used in hospitals differ — see our methodology page.
How often should I recalculate RMR?
When weight, age band, body composition, or training volume changes meaningfully — often every few weeks during active dieting or growth phases.
How is this different from the REE Calculator?
Same seven equations and engine. This page leads with RMR terminology for fitness and weight-management search intent, adds fixed kcal targets and macro preview, and includes pregnancy/clinical disclaimers.
How is this different from the BMR Calculator?
The BMR Calculator compares three formulas without TDEE goals. This RMR hub adds auto-select, all seven equations, TDEE tables, percentage and fixed kcal goals, and macro preview.
Does this store my data?
Inputs may persist in browser local storage for convenience. Calculations run locally; nothing is sent to a server.
Can I compare all formulas at once?
Yes — the results panel shows Mifflin, Harris (original and revised), Katch, Cunningham, Owen, and Schofield when your inputs support each equation.
Why is height optional?
Owen and Schofield do not require height in their core math. Auto-select uses Owen when height is omitted for adults; Mifflin and Harris need height and appear unavailable until height is entered.
What body fat or lean mass should I enter?
Only if you have a reliable estimate (DEXA, BIA, skilled caliper). Guessed body fat reduces accuracy for Katch and Cunningham.
What is Improve Athletic Performance goal?
Not a separate RMR equation. It maps to maintenance calories with guidance to refine TDEE via the Activity Quiz and fuel with the Macro Calculator — performance depends on training, recovery, and timing.
What is Build Muscle goal?
Maps to a mild calorie surplus (+5% of TDEE) with a higher-protein macro preset. Muscle gain also requires progressive resistance training and adequate recovery.
Why does RMR decrease with age?
Lean mass often declines and activity may drop, lowering resting energy. Equations include age terms (except Owen) to approximate this trend — individual variation remains large.
Can thyroid issues affect RMR?
Yes. Hypo- and hyperthyroidism can shift measured resting energy beyond what anthropometric equations predict. Medical conditions require professional assessment — not calculator adjustment.
Is a lower RMR bad for weight loss?
Lower RMR means fewer resting calories, so TDEE may be lower — but fat loss still depends on sustained energy balance, adherence, and protein intake. Trends matter more than a single estimate.
Where do the equations come from?
Peer-reviewed sources: Mifflin (1990), Harris-Benedict (1919/1984), Katch-McArdle (exercise physiology texts), Cunningham (1980), Owen (1986/1987), Schofield/WHO (1985). See the references section on this page.
Is this medical advice?
No. Informational tool for personal awareness and nutrition journaling only — not for prescribing hospital, ICU, enteral feeds, or pregnancy meal plans.
Should I pick Mifflin or Harris-Benedict for RMR?
Mifflin-St Jeor is often preferred for general adults in validation reviews. Harris-Benedict (especially original 1919) may overestimate for many modern adults — useful mainly for comparison.

Research & References

Each citation below supports a specific claim on this page. We explain relevance so you can verify the science yourself.

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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).
  9. 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.
  10. 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.
  11. 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.