The formulas behind the numbers

NutriMeasure uses only long-established, peer-reviewed equations. We don't make up coefficients, we don't use unpublished “proprietary” formulas, and we don't change a published equation without saying so explicitly. Where an equation has a known sex-specific variant, we apply it. Where there's reasonable disagreement between formulas (e.g., BMR or ideal weight), we show the options so you can compare.

Body Mass Index (BMI)

Equation: BMI = weight(kg) / height(m)²

Imperial form: BMI = 703 × weight(lb) / height(in)².

Categoriesfollow the World Health Organization definitions for adults aged 20+: underweight < 18.5; normal 18.5–24.9; overweight 25.0–29.9; obesity 30.0+.

Source: World Health Organization. Physical status: the use and interpretation of anthropometry. WHO Technical Report Series 854, 1995. Confirmed in WHO Expert Consultation, Public Health Nutrition 7(1A), 2004.

Basal Metabolic Rate (BMR)

We offer three equations. The default is Mifflin-St Jeor (1990), which is the most accurate for contemporary healthy adults.

Mifflin-St Jeor (1990) — default

• Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
• Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

Source: Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition 1990;51(2):241–7. doi:10.1093/ajcn/51.2.241

Revised Harris-Benedict (Roza & Shizgal, 1984)

• Men: BMR = 88.362 + 13.397 × weight(kg) + 4.799 × height(cm) − 5.677 × age
• Women: BMR = 447.593 + 9.247 × weight(kg) + 3.098 × height(cm) − 4.330 × age

Source: Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. American Journal of Clinical Nutrition 1984;40(1):168–82. doi:10.1093/ajcn/40.1.168. Original: Harris JA, Benedict FG. A Biometric Study of Basal Metabolism in Man. Carnegie Institution of Washington, 1919.

Katch-McArdle (for known body-fat %)

BMR = 370 + 21.6 × lean body mass(kg), where lean body mass = weight × (1 − body-fat%).

Source: Katch FI, McArdle WD. Nutrition, Weight Control, and Exercise.4th ed. Lippincott Williams & Wilkins, 1993.

Total Daily Energy Expenditure (TDEE)

We multiply BMR by a Physical Activity Level (PAL) factor. The 1.2–1.9 range originates in the Harris-Benedict literature and is the standard used by most dietitians today alongside Mifflin-St Jeor BMR.

• Sedentary (desk job, little exercise): ×1.2
• Lightly active (exercise 1–3 days/week): ×1.375
• Moderately active (3–5 days/week): ×1.55
• Very active (6–7 days/week): ×1.725
• Athlete (twice-daily training, physical job): ×1.9

Reference: Food and Agriculture Organization of the United Nations. Human Energy Requirements. FAO Food and Nutrition Technical Report Series 1, Rome, 2004 — Chapter 5 on PAL values.

Ideal Body Weight

We show four classical formulas side by side. All four use height above 60 inches (152.4 cm) as the scaling anchor.

• Devine (1974): Men 50 kg + 2.3 kg per inch over 5 ft · Women 45.5 kg + 2.3 kg per inch over 5 ft. Original reference: Devine BJ. Gentamicin therapy. Drug Intelligence and Clinical Pharmacy 1974;8:650–5.
• Robinson (1983): Men 52 kg + 1.9 · Women 49 kg + 1.7. Robinson JD, Lupkiewicz SM, Palenik L, et al. American Journal of Hospital Pharmacy 1983;40:1016–9.
• Miller (1983): Men 56.2 kg + 1.41 · Women 53.1 kg + 1.36. Miller DR, Carlson JD, Loyd BJ, Day BJ. Drug Intelligence and Clinical Pharmacy 1983;17:233.
• Hamwi (1964): Men 48 kg + 2.7 · Women 45.5 kg + 2.2. Hamwi GJ. Therapy: Changing dietary concepts. In: Danowski TS, ed. Diabetes Mellitus: Diagnosis and Treatment. American Diabetes Association, 1964.

Calorie Deficit & Weight Loss

We use the Wishnofsky approximation of ~7,700 kcal per kilogram of body fat (3,500 kcal per pound). This is a first-order estimate — in practice, sustained deficits behave differently because metabolism adapts over time. Use it for direction, not a precise weekly-loss guarantee.

Source: Wishnofsky M. Caloric equivalents of gained or lost weight. American Journal of Clinical Nutrition 1958;6(5):542–6. doi:10.1093/ajcn/6.5.542

Safe intake floor: we cap suggested targets at 1,500 kcal (men) / 1,200 kcal (women), aligning with mainstream weight-management guidance and avoiding medically supervised VLCDs (very low calorie diets) below these levels.

Macro Calculator

Energy content per gram (Atwater system):
Protein = 4 kcal/g · Carbohydrate = 4 kcal/g · Fat = 9 kcal/g

Diet preset splits (protein / carbs / fat, % of total kcal):

• Balanced — 30 / 40 / 30
• High-protein — 40 / 35 / 25
• Keto — 25 / 5 / 70
• Mediterranean — 20 / 50 / 30
• Low-carb — 35 / 20 / 45

Protein target for body composition: 1.6–2.2 g/kg per day during a calorie deficit for muscle preservation.

Source: Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition 2014;11:20. doi:10.1186/1550-2783-11-20

Body Fat Percentage (U.S. Navy Tape Method)

All measurements in centimetres.

• Men: BF% = 495 / (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
• Women: BF% = 495 / (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.221 × log₁₀(height)) − 450

Source: Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height. Naval Health Research Center, Report 84-11, 1984. Typically accurate to within ±3% of DEXA for healthy adults.

Body-fat categories follow the American Council on Exercise (ACE) guidelines: essential fat (2–5% men / 10–13% women), athletes, fitness, average, and obese ranges.

Lean Body Mass

Three formulas — kg output, inputs in kg and cm.

• Boer (1984): Men: 0.407 × W + 0.267 × H − 19.2 · Women: 0.252 × W + 0.473 × H − 48.3. Boer P. American Journal of Physiology 1984;247:F632–6.
• James (1976): Men: 1.1 × W − 128 × (W/H)² · Women: 1.07 × W − 148 × (W/H)². James WPT. Research on Obesity. London: HMSO, 1976.
• Hume (1966): Men: 0.32810 × W + 0.33929 × H − 29.5336 · Women: 0.29569 × W + 0.41813 × H − 43.2933. Hume R. Journal of Clinical Pathology 1966;19:389–91.

Waist-to-Height Ratio

WtHR = waist circumference / height (same units). Boundary values used:

• < 0.40 — underweight / slim
• 0.40 – 0.49 — healthy
• 0.50 – 0.59 — overweight / central obesity
• ≥ 0.60 — high metabolic risk

Source: Ashwell M, Gunn P, Gibson S. Waist-to-height ratio is a better screening tool than waist circumference and BMI for adult cardiometabolic risk factors. Obesity Reviews 2012;13(3):275–86. doi:10.1111/j.1467-789X.2011.00952.x

Water Intake

Baseline 35 ml per kg of bodyweight + 500 ml per hour of moderate-to-vigorous exercise + 250 ml (warm) or 500 ml (hot) climate bonus.

Source: European Food Safety Authority Panel on Dietetic Products, Nutrition, and Allergies. Scientific opinion on dietary reference values for water. EFSA Journal 2010;8(3):1459. ESPEN guideline on clinical nutrition in the intensive care unit, Clinical Nutrition 2019;38(1):48–79 uses similar per-kilogram guidance.

One Rep Max (1RM)

Five published formulas. Agreement is within a few percent for 2–10 rep sets; accuracy drops above 10 reps.

• Epley (1985): 1RM = weight × (1 + reps / 30)
• Brzycki (1993): 1RM = weight × 36 / (37 − reps)
• Lander (1985): 1RM = 100 × weight / (101.3 − 2.67123 × reps)
• Lombardi (1989): 1RM = weight × reps^0.10
• O'Conner (1989): 1RM = weight × (1 + 0.025 × reps)

Exercise calories burned (MET-based)

Calories = MET × weight(kg) × hours.

MET (Metabolic Equivalent of Task) values are taken from the 2011 Compendium of Physical Activities, the most widely cited reference.

Source: Ainsworth BE, Haskell WL, Herrmann SD, et al. 2011 Compendium of Physical Activities: a second update of codes and MET values. Medicine & Science in Sports & Exercise 2011;43(8):1575–81. doi:10.1249/MSS.0b013e31821ece12

Unit conversion

Exact SI-defined factors used throughout the site:

• 1 pound = 0.45359237 kilograms (exact, ISO 80000)
• 1 inch = 2.54 centimetres (exact, since 1959)
• 1 foot = 30.48 centimetres (exact)
• 1 mile = 1.609344 kilometres (exact)
• 1 ounce (avdp.) = 28.349523125 grams (exact)

Editorial policy & disclaimer

Every change to a formula on NutriMeasureis logged with a date and reason, and the “last reviewed” date on this page is updated to match.

None of this is medical advice. The formulas here are population-level estimates; your biology, health history, and medications may mean the numbers don't apply to you. Before meaningful changes to your diet, training, or medical care, talk to a GP, dietitian, or qualified healthcare professional.

Found a mistake or a missing reference? Please let us know at nutrimeasureofficial@gmail.com — we take formula accuracy seriously and will correct it with an entry in our change log.

Read about the team →