BMR Calculator
Calculate your Basal Metabolic Rate using Mifflin-St Jeor and Harris-Benedict equations. BMR calculator to find calories burned at rest for weight management.
Reviewed by CalculatorApp.me Health Team
BMR Calculator — Complete Guide
Mifflin–St Jeor, Harris–Benedict, Katch–McArdle equations, TDEE multipliers, and evidence-based calorie planning.
60–75%
BMR share of total calories
1,600
Avg female BMR (kcal/day)
1,900
Avg male BMR (kcal/day)
3
Major BMR equations
What Is Basal Metabolic Rate (BMR)?
Basal Metabolic Rate (BMR) is the minimum number of calories your body burns at complete rest to sustain life — breathing, circulation, cell production, temperature regulation, and neurological function. It represents the energy your body would burn if you lay perfectly still for 24 hours in a thermoneutral environment without eating.
BMR accounts for approximately 60–75% of total daily calorie expenditure for sedentary individuals. The remaining calories come from the Thermic Effect of Food (TEF, ~10%), Non-Exercise Activity Thermogenesis (NEAT, ~15–30%), and intentional exercise. Together these sum to your Total Daily Energy Expenditure (TDEE).
Understanding BMR is the foundation of any effective nutrition strategy. Eating significantly below BMR causes the body to reduce metabolic rate, break down muscle tissue, and enter adaptive thermogenesis — a biological defence against starvation. Most dietitians recommend never eating below BMR long-term.
BMR Equations Compared
Men: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5 Women: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age − 161 Example (Male, 35 years, 80 kg, 178 cm): BMR = 10(80) + 6.25(178) − 5(35) + 5 BMR = 800 + 1112.5 − 175 + 5 BMR = 1,742.5 kcal/day Example (Female, 35 years, 65 kg, 165 cm): BMR = 10(65) + 6.25(165) − 5(35) − 161 BMR = 650 + 1031.25 − 175 − 161 BMR = 1,345.25 kcal/day
Validated in a 2005 American Dietetic Association study as the most accurate predictive equation — within 10% error for 82% of individuals across multiple populations.
Men: BMR = 88.362 + 13.397×wt(kg) + 4.799×ht(cm) − 5.677×age Women: BMR = 447.593 + 9.247×wt(kg) + 3.098×ht(cm) − 4.330×age Example (Male, 35 years, 80 kg, 178 cm): BMR = 88.362 + 13.397(80) + 4.799(178) − 5.677(35) BMR = 88.362 + 1071.76 + 854.222 − 198.695 BMR = 1,815.6 kcal/day Note: ~4% higher than Mifflin–St Jeor Original 1919 equation revised by Roza & Shizgal in 1984 for accuracy.
The 1919 original was re-derived in 1984 using more accurate indirect calorimetry. It tends to overestimate BMR by 4–5% compared to Mifflin–St Jeor, especially in overweight individuals.
BMR = 370 + 21.6 × Lean Body Mass (kg) Lean Mass = Body Weight × (1 − Body Fat %) Example (80 kg, 20% body fat): Lean Mass = 80 × (1 − 0.20) = 64 kg BMR = 370 + 21.6 × 64 BMR = 370 + 1,382.4 BMR = 1,752.4 kcal/day Best for: athletes who know their body fat percentage. Most accurate when body fat % is measured via DEXA or Navy method.
By using lean body mass directly, Katch–McArdle bypasses the sex and weight distortions in Mifflin and Harris–Benedict. It is the preferred equation for athletes with above-average muscle mass.
BMR = 500 + 22 × Lean Body Mass (kg) Example (80 kg, 12% body fat — athlete): Lean Mass = 80 × (1 − 0.12) = 70.4 kg BMR = 500 + 22 × 70.4 BMR = 500 + 1,548.8 BMR = 2,048.8 kcal/day Comparison at same lean mass: Katch–McArdle: 370 + 21.6(70.4) = 1,891 Cunningham: 500 + 22(70.4) = 2,049 Cunningham gives ~8% higher estimate, better calibrated for highly trained athletes with elevated resting metabolic rate due to chronic training adaptations.
Cunningham's equation was derived from athletes and gives higher BMR estimates that better match the elevated resting metabolism seen in highly trained individuals with significant lean mass.
From BMR to TDEE — Activity Multipliers
| Activity Level | Multiplier | Description | TDEE (BMR=1,750) |
|---|---|---|---|
| Sedentary | × 1.2 | Desk job, little/no exercise | 2,100 kcal |
| Lightly Active | × 1.375 | Light exercise 1–3 days/week | 2,406 kcal |
| Moderately Active | × 1.55 | Moderate exercise 3–5 days/week | 2,713 kcal |
| Very Active | × 1.725 | Hard exercise 6–7 days/week | 3,019 kcal |
| Extra Active | × 1.9 | Physical job + twice-daily training | 3,325 kcal |
Practical tip: Most people overestimate their activity level by one category. If you think you are "very active", start with "moderately active" and adjust upward based on actual weight changes over 2–3 weeks. TDEE estimates are population averages — individual variation can be ±15–20%.
Using BMR & TDEE for Diet Planning
Weight Loss
- •Eat 300–500 kcal below TDEE
- •Aim for 0.5–1 kg loss per week
- •Never eat below BMR long-term
- •Protein intake ≥ 1.6 g/kg body weight
Weight Maintenance
- •Eat at TDEE
- •Adjust weekly by ±100–200 kcal
- •Track weight trends, not daily changes
- •Reassess BMR every 3 months
Muscle Gain
- •Eat 200–300 kcal above TDEE
- •Target ≥ 1.8 g protein per kg
- •Expect 0.25–0.5 kg/month lean gain
- •Limit surplus to minimise fat gain
BMR Myths vs. Facts
Myth: Eating less always speeds up fat loss
Fact: Severe calorie restriction below BMR triggers adaptive thermogenesis — the body reduces BMR by 15–30% to conserve energy. This is why crash diets cause metabolic slowdown and rapid weight regain.
Myth: BMR stays constant throughout life
Fact: BMR declines approximately 1–2% per decade after age 30, primarily due to muscle loss. Resistance training is the most effective strategy to maintain a higher BMR with age.
Myth: Small meals 'stoke' the metabolism
Fact: Meal frequency has no significant effect on BMR or TDEE when total calories are matched. The thermic effect of food depends on total daily protein and calorie intake, not how it is distributed.
Myth: Cardio is the best way to raise BMR
Fact: While cardio burns calories during exercise, resistance training builds muscle mass — the primary driver of resting metabolic rate. One kg of muscle burns ~13 kcal/day at rest vs. ~4 kcal for fat.
Frequently Asked Questions
What is the difference between BMR and RMR?▼
BMR (Basal Metabolic Rate) is measured under strict conditions: complete rest, thermoneutral environment, 12-hour fast, no recent exercise. RMR (Resting Metabolic Rate) is measured under less restrictive conditions and is typically 10–20% higher than true BMR. Most online calculators technically estimate RMR, though they call it BMR.
What is my BMR if I am overweight?▼
BMR is largely driven by lean body mass (muscle and organs), not total weight. An overweight person has more lean mass supporting their larger frame, so their absolute BMR is typically higher than a lighter person. However, per kg of body weight, their BMR may be lower if excess weight is mostly fat.
Does BMR change on a low-calorie diet?▼
Yes. Studies show that extended calorie restriction (>4 weeks below BMR) reduces BMR by 10–30% through adaptive thermogenesis. This is separate from the reduction caused by losing weight. Refeed days or 'diet breaks' can partially mitigate this metabolic adaptation.
How accurate are BMR calculators?▼
The Mifflin–St Jeor equation is accurate to within 10% for approximately 82% of individuals when compared to indirect calorimetry (the gold standard). Individual variation due to genetics, thyroid function, medications, and health conditions means your true BMR may differ significantly from any formula's prediction.
References & Clinical Sources
- Mifflin MD, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–7.
- Roza AM, Shizgal HM. The Harris–Benedict equation reevaluated. Am J Clin Nutr. 1984;40(1):168–82.
- Katch V, et al. Prediction of body composition from BMI and non-weight measurements. Med Sci Sports Exerc. 1986.
- Frankenfield D, et al. Comparison of predictive equations for resting metabolic rate in healthy adults. J Am Diet Assoc. 2005;105(5):775–89.
- Speakman JR, Selman C. Physical activity and resting metabolic rate. Proc Nutr Soc. 2003;62(3):621–34.
Methodology, sources & limitations
This calculator uses a published formula and the values entered in the calculator to generate the result.
- Formula
- BMR = 10×weight(kg) + 6.25×height(cm) − 5×age − 161 (female) or +5 (male)
- Jurisdiction & units
- Intended for US, IN, EU, GB, AU, CA, Global. Supports both units where applicable.
- Assumptions & limitations
- Results are screening or educational estimates based on the inputs you provide. They do not diagnose, treat, or replace advice from a qualified clinician.
- Review status
- Formula and automated QA completed June 21, 2026; independent professional review is pending. Next scheduled review: September 21, 2026.
Validation sources
- Mifflin et al. (1990)
- American Dietetic Association
BMR Calculator — Answer & Method
Calculate Basal Metabolic Rate using the Mifflin-St Jeor equation. Determines daily calorie needs at rest.
Formula: Basal Metabolic Rate (Mifflin-St Jeor)
BMR = 10×weight(kg) + 6.25×height(cm) − 5×age − 161 (female) or +5 (male)
Example Calculation
A 30-year-old male weighing 70 kg at 175 cm has a BMR of approximately 1,649 kcal/day.
Important limitation
This is an educational estimate, not a diagnosis or a substitute for professional medical advice.
Key Facts
- The Mifflin-St Jeor equation is considered the most accurate BMR formula by the American Dietetic Association.
- BMR accounts for 60-75% of daily total energy expenditure.
- TDEE is calculated by multiplying BMR by an activity factor ranging from 1.2 (sedentary) to 1.9 (extremely active).