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HomeCalculatehealth/bmr-calculator

BMR Calculator

Estimate the calories your body burns at rest from weight, height, age, and sex, using the Mifflin-St Jeor equation.

Health tools disclaimer

Results are educational estimates based on the formulas and inputs shown. They are not medical advice, diagnosis, or treatment. For clinical decisions, medication dosing, or emergency symptoms, consult a licensed healthcare professional.

Related calculators

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Verification & transparency

Automated checks: engine-validated output
Last updated:2026-09-01
|
Sources:WHO 2024 · CDC Growth Charts · Mifflin-St Jeor 1990 · IOM 2009 Weight Gain
|
Reference:bmr = 10 * weightKg + 6.25 * heightCm - 5 * ageYears + sexConstant
|Rounding & precision policy
Inputs Reference
  • Weight (kg)
  • Height (cm)
  • Age (years)
  • Sex constant
Formula

bmr = 10 * weightKg + 6.25 * heightCm - 5 * ageYears + sexConstant

On This Page
  • Primary output (BMR)
  • Calculator inputs
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Imperial

Body metrics

BMR1 617.50cal/day
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BMR Calculator | ExpertToolkit
  • Reverse solve
  • Formula and method
  • Computation graph
  • BMR decision comparison
  • Result chart
    • Common Questions
    • Why does this page use Mifflin-St Jeor rather than Harris-Benedict?
    • How different are the male and female results, and why?
    • Does metabolism really slow with age?
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    • BMR Calculatorgraph

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    © 2026 ExpertToolkit. All rights reserved.

    Release 2.5Market: United States

    Primary output (BMR)

    BMR

    1617.5

    Computed from default inputs using graph `synth-bmr-calculator`.

    Calculator inputs

    Weight
    70 kg
    Range: 20 - 300

    Mathematical model

    bmr = 10 * weightKg + 6.25 * heightCm - 5 * ageYears + sexConstant

    Main equation used by this calculator. Numeric steps follow the page's precision and rounding rules.

    Term Glossary

    Weight
    Weight is a declared input for BMR Calculator, measured in kg. Check this value and its unit before reusing the result.
    Sources & Standards
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    Height
    170 cm
    Range: 50 - 250
    Age
    30 years
    Range: 1 - 120
    Sex constant
    5
    Range: -161 - 5

    BMR Calculator | ExpertToolkit

    25 × height (cm) − 5 × age + 5 for males, or −161 for females. Published in 1990 from measurements of 498 adults, it replaced the 1919 Harris-Benedict equation as the standard predictive formula after reviews — including the American Dietetic Association's 2005 evidence analysis — found it the most accurate for the general population, with Harris-Benedict overestimating by roughly 5 %. The number it produces is basal metabolic rate: the energy cost of staying alive at complete rest.

    Reverse solve

    Solve for Weight

    Weight: 86.175 for BMR 1.779e+3

    Formula and method

    Mifflin-St Jeor basal metabolic rate estimate.

    bmr=10⋅weightKg+6.25⋅heightCm−5⋅ageYears+sexConstant bmr=10\cdot weightKg+6.25\cdot heightCm-5\cdot ageYears+ sexConstantbmr=10⋅weightKg+6.25⋅heightCm−5⋅ageYears+sexConstant

    Computation graph

    1. bmr10 * weightKg + 6.25 * heightCm - 5 * ageYears + sexConstant

    BMR decision comparison

    BMR decision comparison

    itemvaluenote
    Stress low1117.5Weight: 20
    Conservative1442.5Weight: 52.5
    Downside1547.5Weight: 63
    Base case1617.5Weight: 70
    Upside1687.5Weight: 77

    Result chart

    Visual Analysis1 series8 points

    Expanded chart built from the same sensitivity run as the table, so users can read the trend and verify the numbers in one place.

    Trend
    Upward
    Min
    1.1K
    Max
    3.3K
    Insight
    BMR shows an upward pattern, with a visible peak around 237.7778 at 3.3K.
    1.1K1.7K2.2K2.8K3.3K2051.111182.2222113.3333144.4444175.5556206.6667237.7778

    Visual response curve for BMR.

    Worked examples: the BMR calculator

    From BMR to a daily calorie target
    A 35-year-old woman, 165 cm and 68 kg: BMR = 10 × 68 + 6.25 × 165 − 5 × 35 − 161 = 1,376 kcal. Training three days a week puts her near the 1.375 multiplier: about 1,892 kcal maintenance. A 15 % deficit for fat loss lands near 1,600 kcal — comfortably above her BMR, which is how the two numbers are meant to relate.

    the BMR calculator — frequently asked questions

    Why does this page use Mifflin-St Jeor rather than Harris-Benedict?
    Comparative studies consistently rank Mifflin-St Jeor closest to measured resting energy expenditure in modern adults — the ADA's systematic review found it accurate within 10 % for more subjects than any competitor. Harris-Benedict, derived a century ago from a smaller and leaner sample, reads about 5 % high for today's population. The +5/−161 sex constant in the input reflects the published equation exactly.
    How different are the male and female results, and why?
    The equations differ by a constant 166 kcal (the gap between +5 and −161), reflecting average body-composition differences in the derivation sample — lean mass drives metabolism, and the sex constant is a proxy for it. Individuals with measured body fat can get closer with lean-mass equations (Katch-McArdle), which this page's plain inputs deliberately avoid requiring.
    Does metabolism really slow with age?
    In this equation, by 5 kcal per year — about 50 kcal per decade, mostly tracking gradual lean-mass loss rather than aging itself. Recent large-scale work (Pontzer et al., 2021) suggests adjusted metabolic rate is stable from roughly age 20 to 60, with the practical implication that staying active and keeping muscle largely neutralizes the age term.

    How to use this calculator

    Health tools disclaimer: Educational estimates only, not medical advice, diagnosis, or treatment. For clinical decisions, dosing, or emergencies, follow guidance from US Department of Health & Human Services and a licensed professional in your jurisdiction.

    Estimate daily resting calorie needs with the Mifflin-St Jeor equation.

    BMR Calculator turns Weight, Height, Age, and Sex constant into BMR. Confirm the units and assumptions match your situation before relying on the result.

    1. Enter weight and height. Use a measured morning weight and measured height. In the Mifflin-St Jeor equation each kilogram changes BMR by 10 kcal/day, so a rough guess shifts the result meaningfully.
    2. Enter age and sex. The equation subtracts 5 kcal/day per year of age, and the sex constant differs by 166 kcal/day (+5 men, −161 women) — both fields materially change the estimate.
    3. Check the units. The formula expects kilograms and centimetres. If you work in pounds and inches, use the unit selector — 180 lb entered as kilograms overstates BMR by roughly 1,000 kcal/day.
    4. Read BMR, then apply an activity factor. BMR alone is resting energy. Total daily energy expenditure (TDEE) = BMR × activity factor: 1.2 sedentary, 1.375 light (1–3 days/week), 1.55 moderate (3–5 days), 1.725 heavy (6–7 days).
    5. Treat the output as a starting estimate. Prediction equations carry roughly ±10% error for individuals. Compare the estimate against 2–4 weeks of actual intake and weight trend, then adjust.

    Overwhelm from technical jargon

    Start with the basic inputs only — advanced options can be explored once you understand the fundamentals. Important: Don't be discouraged if your results seem unfavorable — these tools help you plan, not judge.

    Enter your values, then check the formula, scenarios, and FAQ to confirm the assumptions fit your case. For medical, financial, legal, or safety-critical decisions, treat the output as an estimate and verify it against the relevant professional standard.

    Sources & Standards

    1. World Health Organization. "Body mass index - BMI." WHO Regional Office for Europe, 2024.BMI classification thresholds: underweight <18.5, normal 18.5-24.9, overweight 25-29.9, obese ≥30
    2. Centers for Disease Control and Prevention. "About Child & Teen BMI." CDC, 2024.Pediatric BMI uses age-sex-specific percentiles, not adult thresholds
    3. Mifflin MD, St Jeor ST, et al. "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr. 1990;51(2):241-247.BMR formula: 10×weight(kg) + 6.25×height(cm) - 5×age - 161 (female) or +5 (male)
    4. Institute of Medicine. "Weight Gain During Pregnancy: Reexamining the Guidelines." National Academies Press, 2009.Recommended pregnancy weight gain by pre-pregnancy BMI category

    Verify this result

    This answer is computed by CalculationEngine (v1.0.0). The same inputs always produce the same figure and the same fingerprint below, so you can reproduce and cite it.

    Standards

    • WHO 2024 — BMI classification thresholds: underweight <18.5, normal 18.5-24.9, overweight 25-29.9, ob
    • CDC Growth Charts — Pediatric BMI uses age-sex-specific percentiles, not adult thresholds
    • Mifflin-St Jeor 1990 — BMR formula: 10×weight(kg) + 6.25×height(cm) - 5×age - 161 (female) or +5 (male)

    Assumptions

    • Scenariodefault inputs
    • Methodformula-graph evaluation
    • Formulabmr = 10 * weightKg + 6.25 * heightCm - 5 * ageYears + sexConstant

    Inputs & outputs

    • in · weightKg70
    • in · heightCm170
    • in · ageYears30
    • in · sexConstant5
    • out · BMR1617.5

    Computation fingerprint (SHA-256)

    2e73e46ed7748250f733c05f8d4b0b66a7f4ca234bb4b8a36e6a2e05d0b6f1da

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    BMI CalculatorgraphAll calculatorshub

    BMR Calculator context FAQ

    When is this health estimation context enough?
    Use it when the result only depends on age, sex, height and no local rule changes the interpretation.
    What should I record with the result?
    Record the input values, reference population, measurement unit, activity estimate, output unit, and rounding rule used in the calculation.
    When should I use a specialized modifier?
    Use a specialized modifier when measurement units, reference range, age/sex context, and non-diagnostic limits materially changes how the same result should be explained.

    Common mistakes with the BMR calculator

    Eating at BMR to lose weight. BMR is the floor, not a target: sustained intake below it is neither necessary nor advisable for typical fat-loss goals, which are set relative to total daily expenditure (BMR × activity), usually at a 10–25 % deficit.
    Choosing an aspirational activity multiplier. Most desk workers who train three times a week are 1.375–1.55, not 1.725. Overstating activity by one tier adds 300–400 phantom calories to the estimate — more than the deficit many plans rely on.
    Height
    Height is a declared input for BMR Calculator, measured in cm. Check this value and its unit before reusing the result.
    Age
    Age is a declared input for BMR Calculator, measured in years. Check this value and its unit before reusing the result.
    Sex constant
    Use 5 for male and -161 for female in Mifflin-St Jeor.
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    X-axis: WeightY-axis: BMR