BMR Calculator — Mifflin-St Jeor Equation
Calculate your Basal Metabolic Rate instantly with the Mifflin-St Jeor formula. Get your BMR + TDEE by activity level. Includes reference table for men and women by age and weight.
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Reviewed by: Martín Rodríguez (editorial policy ) · Last reviewed:
Result
Basal Metabolic Rate (BMR)
Total Daily Energy Expenditure (TDEE)
Activity Multiplier
Weight Used
Height Used
Formula Applied
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For guidance only — not medical advice. Consult a licensed healthcare professional.
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Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to sustain vital functions — breathing, circulation, temperature regulation, and cell repair. The Mifflin-St Jeor equation (published 1990) is consistently rated the most accurate predictive formula for healthy adults in clinical literature, outperforming the older Harris-Benedict formula. Enter your sex, weight, height, and age to get your BMR and Total Daily Energy Expenditure (TDEE) based on your activity level — the two numbers you actually need to set a calorie goal.
When to use this calculator
- Setting a science-backed calorie target for weight loss or muscle gain
- Estimating how many calories to eat on rest days vs. training days
- Comparing BMR changes after significant weight loss or gain
- Supporting a dietitian or nutritionist consultation with baseline data
- Tracking metabolic changes with age over multiple years
Activity Multipliers for TDEE (Mifflin-St Jeor)
| Activity Level | Multiplier | Description |
|---|---|---|
| Sedentary | 1.200 | Desk job, no structured exercise |
| Lightly active | 1.375 | Light cardio or weights 1–3 days/week |
| Moderately active | 1.550 | Moderate workouts 3–5 days/week |
| Very active | 1.725 | Hard training 6–7 days/week |
| Extra active | 1.900 | Twice-daily training or labor-intensive job |
Fuente: Mifflin MD et al., American Journal of Clinical Nutrition (1990); escala de actividad Harris-Benedict adoptada en la literatura clínica estándar.
How it works
What is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate is the number of calories your body burns at complete rest — lying still, not digesting food. It represents roughly 60–75% of total daily energy expenditure for most people. The Mifflin-St Jeor equation, developed in 1990, is the clinical gold standard for estimating BMR in healthy adults.
The Mifflin-St Jeor Formula
// Male
BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) + 5
// Female
BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) − 161
// TDEE
TDEE = BMR × activity_factorUnit conversions applied automatically:
BMR Reference Table — Women (165 cm / 5′5″)
| Age | 55 kg (121 lb) | 65 kg (143 lb) | 75 kg (165 lb) | 85 kg (187 lb) |
|---|---|---|---|---|
| 25 | 1,327 kcal | 1,427 kcal | 1,527 kcal | 1,627 kcal |
| 35 | 1,277 kcal | 1,377 kcal | 1,477 kcal | 1,577 kcal |
| 45 | 1,227 kcal | 1,327 kcal | 1,427 kcal | 1,527 kcal |
| 55 | 1,177 kcal | 1,277 kcal | 1,377 kcal | 1,477 kcal |
| 65 | 1,127 kcal | 1,227 kcal | 1,327 kcal | 1,427 kcal |
BMR Reference Table — Men (178 cm / 5′10″)
| Age | 70 kg (154 lb) | 80 kg (176 lb) | 90 kg (198 lb) | 100 kg (220 lb) |
|---|---|---|---|---|
| 25 | 1,758 kcal | 1,858 kcal | 1,958 kcal | 2,058 kcal |
| 35 | 1,708 kcal | 1,808 kcal | 1,908 kcal | 2,008 kcal |
| 45 | 1,658 kcal | 1,758 kcal | 1,858 kcal | 1,958 kcal |
| 55 | 1,608 kcal | 1,708 kcal | 1,808 kcal | 1,908 kcal |
| 65 | 1,558 kcal | 1,658 kcal | 1,758 kcal | 1,858 kcal |
Activity Multipliers (Harris-Benedict scale)
| Level | Multiplier | Description |
|---|---|---|
| Sedentary | 1.200 | Desk job, no structured exercise |
| Lightly active | 1.375 | Light cardio or weights 1–3 days/week |
| Moderately active | 1.550 | Moderate workouts 3–5 days/week |
| Very active | 1.725 | Hard training 6–7 days/week |
| Extra active | 1.900 | Twice-daily training or labor-intensive job |
Worked Example
Female, 154 lb (69.9 kg), 5′5″ (165.1 cm), age 35, sedentary:
BMR = (10 × 69.9) + (6.25 × 165.1) − (5 × 35) − 161
= 699 + 1,031.9 − 175 − 161
= 1,394.9 ≈ 1,395 kcal/day
TDEE = 1,395 × 1.2 = 1,674 kcal/dayFor weight loss at 1 lb/week: 1,674 − 500 = 1,174 kcal/day.
Why Mifflin-St Jeor over Harris-Benedict?
The Harris-Benedict equation (1919) was built on a sample of just 239 subjects. The Mifflin-St Jeor equation (1990) studied 498 healthy adults using indirect calorimetry (the laboratory gold standard). A 2005 meta-analysis in the Journal of the American Dietetic Association found Mifflin-St Jeor predicted resting energy expenditure within 10% of measured values in 82% of non-obese subjects vs. roughly 68% for Harris-Benedict.
Limitations
Disclaimer: Los resultados son orientativos y no reemplazan la consulta médica profesional. Antes de tomar decisiones con impacto, consultá con un médico, nutricionista o profesional de la salud matriculado.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the calories your body needs at complete rest — no movement, no digestion. TDEE (Total Daily Energy Expenditure) adds the calories burned through all daily activity on top of BMR. Eating at your TDEE maintains your current weight; eating below it creates a deficit for weight loss.
What is the exact Mifflin-St Jeor formula?
For men: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) + 5. For women: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) − 161. TDEE = BMR × activity factor (1.2 to 1.9 depending on exercise level).
Why is Mifflin-St Jeor considered more accurate than Harris-Benedict?
Harris-Benedict was developed in 1919 on a small sample. Mifflin-St Jeor (1990) used a larger, more diverse modern cohort. A 2005 Academy of Nutrition and Dietetics review found Mifflin-St Jeor predicted measured REE within 10% for about 82% of subjects vs. roughly 68% for Harris-Benedict.
How do I choose the right activity level?
Be honest and conservative — most people overestimate activity. Desk job with occasional walks = Sedentary. Gym 2–3x/week = Lightly active. Regular workouts 4–5 days = Moderately active. Daily intense training = Very active. Twice-daily training or physical labor = Extra active.
Can I use this calculator to set a weight-loss calorie goal?
Yes. A common starting point is TDEE minus 500 kcal/day, which produces roughly 1 lb (0.45 kg) of fat loss per week. Avoid eating below your BMR without medical supervision, as severe restriction reduces muscle mass and lowers metabolic rate over time.
Does BMR decrease with age?
Yes. The Mifflin-St Jeor formula subtracts 5 × age from BMR. A 60-year-old man has a BMR roughly 125 kcal/day lower than a 35-year-old with identical weight and height. Loss of muscle mass (sarcopenia) with age contributes an additional real-world decrease beyond the formula's estimate.
Is this calculator accurate for athletes with high muscle mass?
The Mifflin-St Jeor equation does not account for body composition directly. Highly muscular individuals may have a higher actual BMR than the formula predicts, because lean muscle burns more calories at rest than fat. For athletes, the Katch-McArdle formula (which uses lean body mass) may be more precise.
What units does this calculator accept?
You can enter weight in pounds (lb) or kilograms (kg), and height in inches (in) or centimeters (cm). The calculator automatically converts to metric before applying the Mifflin-St Jeor formula, which is defined in SI units (kg and cm).
How often should I recalculate my BMR?
Recalculate whenever your weight changes by more than 5 lb (2.3 kg), after a significant change in activity level, or yearly since age is a continuous variable in the formula. People actively cutting or bulking should recalculate every 4–6 weeks.
Does the formula work for people over 65?
The Mifflin-St Jeor equation can be used for older adults, but accuracy decreases with age due to greater variability in body composition. It may underestimate energy needs in very lean elderly individuals. Consult a registered dietitian for personalized recommendations in this population.
Sources & references
- Mifflin MD et al. — A new predictive equation for resting energy expenditure in healthy individuals (1990) — American Journal of Clinical Nutrition / PubMed (1990)
- Frankenfield D et al. — Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults (2005) — Journal of the American Dietetic Association / PubMed (2005)
- NIH — Body Weight Planner — National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (2026)
- CDC — Healthy Weight, Nutrition, and Physical Activity — Centers for Disease Control and Prevention (2026)
Methodology & trust
Editorial
Calculadora de salud revisada por el equipo editorial de Hacé Cuentas, contrastada con Mifflin MD et al. — A new predictive equation for resting energy expenditure in healthy individuals (1990), según nuestra política editorial y metodología.
Updates
Última revisión: June 20, 2026. Los parámetros se verifican periódicamente con las fuentes citadas.
Privacy
Calculations run 100% in your browser. We do not store or transmit your data.
Limitations
Indicative results. For critical decisions, consult a professional.
📌 How to cite this calculator
Rodríguez, M. (2026). BMR Calculator — Mifflin-St Jeor Equation. Hacé Cuentas. https://hacecuentas.com/bmr-mifflin-st-jeor-calculator
Contenido bajo licencia CC-BY 4.0 — reutilizable citando la fuente con enlace a Hacé Cuentas.