Verified Body Metric Formulas & Health Standards
Why This Page Exists
Every formula and range below is drawn from a named, published source — a peer-reviewed paper, a U.S. government agency (CDC, NIH), the World Health Organization (WHO), or a professional certifying body (the American Council on Exercise, ACE). Where a value is an estimate rather than a measured fact, we say so. Use this page as the single source of truth behind VivMetric's calculators.
Body-composition and metabolism calculators are only as trustworthy as the math and the reference values behind them. This reference page documents exactly what VivMetric uses, who published it, and where you can verify it yourself. We cover four core areas: basal metabolic rate (BMR) formulas, total daily energy expenditure (TDEE) multipliers, body-fat percentage reference ranges, and the official BMI and waist-circumference standards from WHO, CDC, and NIH.
1. BMR Formulas (Resting Metabolism)
BMR is the calories your body burns at complete rest to keep you alive — breathing, circulation, cell repair. It is the foundation of every calorie and TDEE estimate. Two prediction equations dominate clinical and public-health practice.
1a. Mifflin-St Jeor (1990) — the current standard
Published in the American Journal of Clinical Nutrition by Mifflin, St Jeor, Hill, Scott, Daugherty, and Koh (1990), this equation is the one the Academy of Nutrition and Dietetics identifies as the most accurate population-level BMR predictor. It is the default formula in VivMetric's BMR Calculator.
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(years) − 161
Source: 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):241–7. PubMed ID 2305711.
1b. Harris-Benedict (1918/1919, revised 1984)
The original Harris-Benedict equations were published by James Arthur Harris and Francis Gano Benedict in A Biometric Study of Basal Metabolism in Man (Carnegie Institution of Washington, publication no. 279, 1919), based on measurements of 239 adults. Because that sample was narrow, Roza and Shizgal re-estimated the coefficients in 1984 using a larger, more diverse dataset — the version most calculators use today.
Revised Harris-Benedict — Men: BMR = 88.362 + 13.397 × weight(kg) + 4.799 × height(cm) − 5.677 × age(years)
Revised Harris-Benedict — Women: BMR = 447.593 + 9.247 × weight(kg) + 3.098 × height(cm) − 4.330 × age(years)
Source: Roza AM, Shizgal HM. "The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass." Am J Clin Nutr. 1984;40(1):168–82. PubMed ID 6741850.
1c. Katch-McArdle (lean-mass based)
Unlike the equations above, Katch-McArdle uses lean body mass instead of total weight, so it is less biased by high or low body-fat levels: BMR = 370 + 21.6 × lean body mass(kg). It is included in the BMR Calculator as a conditional option for users who know their lean mass.
2. TDEE Activity Multipliers (1.2–1.9)
Total Daily Energy Expenditure is estimated by multiplying BMR by an activity factor. The multiplier set below is the most widely used framework in clinical and fitness practice for describing activity levels. These multipliers are practical estimates, not the output of a single randomized trial — an individual's true TDEE can vary by roughly ±10–20% around the estimate because of genetics, NEAT (non-exercise activity thermogenesis), and diet-induced thermogenesis.
| Multiplier | Activity Description |
|---|---|
| 1.2 | Sedentary — little or no exercise, desk job |
| 1.375 | Lightly active — light exercise/sports 1–3 days/week |
| 1.55 | Moderately active — moderate exercise/sports 3–5 days/week |
| 1.725 | Very active — hard exercise/sports 6–7 days/week |
| 1.9 | Extra active — very hard daily exercise, physical job, or training twice a day |
The underlying activity levels map to the U.S. Centers for Disease Control and Prevention (CDC) physical-activity guidelines, which recommend adults aim for at least 150 minutes of moderate-intensity activity per week. For defining your own level, see the CDC adult physical-activity basics. The BMR × multiplier approach is consistent with the energy-requirements framework described by the FAO/WHO/UNU expert consultation (2004): Human Energy Requirements, FAO/WHO/UNU.
3. Body Fat Percentage Reference Ranges (ACE)
The American Council on Exercise (ACE) publishes the practitioner reference bands most widely used in the fitness industry. These are population-level reference points, not diagnostic thresholds. VivMetric's Body Fat Calculator labels results using these bands.
| Category | Men (%) | Women (%) |
|---|---|---|
| Essential fat | 2–5 | 10–13 |
| Athletes | 6–13 | 14–20 |
| Fitness | 14–17 | 21–24 |
| Acceptable | 18–24 | 25–31 |
| Obese | 25+ | 32+ |
Source: American Council on Exercise, professional body-composition resources — see ACE's explainer, "Your Guide to Body Composition". Going below essential-fat levels is a clinical concern, not a fitness goal.
4. WHO / CDC BMI Classification
Body Mass Index is a screening measure, not a diagnostic one. The World Health Organization defines these adult categories (age 20+), which the U.S. CDC adopts for the American population.
| Category | BMI (kg/m²) |
|---|---|
| Underweight | < 18.5 |
| Normal | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese (Class I) | 30.0 – 34.9 |
| Obese (Class II) | 35.0 – 39.9 |
| Obese (Class III) | ≥ 40.0 |
Sources: WHO fact sheet "Obesity and overweight"; CDC Adult BMI. Several Asian public-health authorities use lower cutoffs because metabolic risk rises at lower BMI in those populations — see our BMI formula guide for the details.
5. Waist Circumference Risk Cutoffs (WHO / NIH)
Because BMI ignores fat distribution, waist circumference is used alongside it to flag central (abdominal) adiposity. Two sets of cutoffs are in common use:
- NIH / NHLBI (U.S.): increased risk at waist ≥ 102 cm (40 in) for men and ≥ 88 cm (35 in) for women. Source: NHLBI Aim for a Healthy Weight.
- WHO: "increased" risk at ≥ 94 cm (men) / ≥ 80 cm (women), and "substantially increased" risk at ≥ 102 cm (men) / ≥ 88 cm (women). Source: WHO anthropometry report (WHO Technical Report Series 854, 1995): Physical status: the use and interpretation of anthropometry.
6. Worked Example: BMR → TDEE
Take a 30-year-old woman, 154 lb (70 kg), 5'9" (175 cm), moderately active:
Mifflin-St Jeor BMR: (10 × 70) + (6.25 × 175) − (5 × 30) − 161 = 700 + 1093.75 − 150 − 161 = 1,482.75 kcal/day.
TDEE at 1.55 (moderately active): 1,482.75 × 1.55 ≈ 2,298 kcal/day.
A gentle fat-loss target would typically sit a few hundred kcal below TDEE; a maintenance target sits at TDEE. These remain estimates — confirm any plan with a qualified professional.
7. Known Limitations (Read Before You Trust a Number)
- Prediction error: BMR equations are population regressions; for an individual they can miss measured values by 100–280 kcal/day, and error grows at very low or very high BMI.
- Reference ranges are not diagnoses: ACE and WHO bands describe populations. A single person can be healthy outside them, or at risk inside them.
- Body-fat formulas are estimates: circumference-based methods (Deurenberg, US Navy) typically land within about 3–5 percentage points of DEXA, the clinical gold standard.
- Not for medical use: none of these tools should replace a clinician's assessment, lab work, or diagnosis.