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 vs. RMR vs. TDEE
| Term | Definition | Includes Activity? | Used For |
|---|---|---|---|
| BMR | Calories burned completely at rest (awake, fasted) | No | Research baseline |
| RMR | Resting energy measured under less restrictive conditions than BMR | No | Clinical measurements |
| TDEE | Total Daily Energy Expenditure including all activity | Yes | Estimating total daily expenditure |
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.
Limitations
This calculator estimates resting energy expenditure using the Mifflin–St Jeor equation — it does not measure your actual metabolism. Indirect calorimetry is the only way to directly measure BMR; an individual's true value can reasonably fall more than 10% above or below this estimate.
The result is not a calorie prescription. Health conditions, medications, thyroid function, pregnancy, and body composition all affect resting energy expenditure in ways this formula cannot account for — anyone planning a substantial calorie or weight change should get individualized guidance from a physician or registered dietitian rather than treating this estimate as a target.
Frequently Asked Questions
What is Basal Metabolic Rate (BMR)?▼
Basal metabolic rate is the energy your body uses under strict resting, fasting, and temperature-controlled conditions. An online BMR calculator does not measure that rate; it estimates resting energy expenditure from age, sex, height, and weight.
What is the Mifflin-St Jeor equation?▼
The Mifflin-St Jeor equation, published in 1990, predicts resting energy expenditure. For males: 10W + 6.25H − 5A + 5. For females: 10W + 6.25H − 5A − 161, where W is kilograms, H is centimetres, and A is years. Validation studies show useful group-level performance, but an individual estimate may be more than 10% above or below a measured value.
What is the Harris-Benedict equation?▼
The original Harris-Benedict equation was introduced in 1919 and revised in 1984. Revised formula for males: BMR = 88.362 + (13.397 × W) + (4.799 × H) − (5.677 × A). For females: BMR = 447.593 + (9.247 × W) + (3.098 × H) − (4.330 × A). While still widely used, studies show the Mifflin-St Jeor equation is more accurate for modern populations, which tend to be more sedentary.
What is the difference between BMR and TDEE?▼
BMR describes energy expenditure under basal conditions. TDEE includes resting expenditure, movement, exercise, and the energy used to process food. This tool estimates TDEE by multiplying its BMR estimate by an activity factor, so TDEE has additional uncertainty and is not a prescribed calorie target.
How does age affect BMR?▼
Age is one input in the Mifflin-St Jeor equation, but changes in body size, body composition, health, and other factors also affect resting energy expenditure. The calculator cannot determine why an individual result changes over time.
Does muscle mass increase BMR?▼
Lean mass is one contributor to resting energy expenditure, but the effect for an individual cannot be calculated from muscle mass alone. This calculator does not use body-composition data, so results may differ for people whose body composition differs from the populations used to develop the equation.
Is BMR the same as Resting Metabolic Rate (RMR)?▼
They are related but not identical. BMR is measured under stricter standardized conditions than resting metabolic rate (RMR). The Mifflin-St Jeor equation was developed to predict resting energy expenditure, so this page uses the familiar search term “BMR calculator” while labeling the output as an estimate.
How do I use my BMR to lose weight?▼
Do not treat the BMR result as a calorie prescription. A TDEE estimate can be a starting point for monitoring, but calorie needs and appropriate changes depend on health, medications, pregnancy, activity, and goals. Seek individualized advice from a qualified clinician or registered dietitian if planning substantial weight change.
How many calories do I burn at rest each day?▼
There is no single normal BMR for all adults. Resting energy expenditure varies with age, sex, height, weight, body composition, health, and measurement conditions. This calculator provides an equation-based estimate, not a metabolic measurement.
Can I increase my BMR?▼
Resting energy expenditure can change with body size, body composition, age, health, and other factors, but a calculator cannot predict how a particular intervention will change it. Use the result as an estimate rather than a treatment target.
Which BMR formula is most accurate?▼
No prediction equation is most accurate for every person or population. This calculator uses Mifflin-St Jeor because it has been widely studied in adults. Indirect calorimetry measures resting energy expenditure and may be more appropriate when clinical precision matters.
What makes a BMR calculator the best choice for estimating resting calories?▼
The most useful BMR calculators use a formula with strong population-level validation rather than an outdated or non-standard equation. This calculator applies the Mifflin-St Jeor equation (1990), which research has generally found more accurate for the modern population than the older 1919 Harris-Benedict formula. No BMR calculator measures your actual metabolism — only indirect calorimetry does that — so treat the result as a well-supported estimate, not a lab measurement.
How does sex affect BMR?▼
The published Mifflin-St Jeor equation uses different constants for males and females. These are population-based equation inputs and do not directly measure hormones, anatomy, or body composition, so they can add uncertainty for an individual.
How many calories are in a pound of body fat?▼
The commonly cited estimate is that one pound of body fat represents roughly 3,500 kcal of energy. This is a population-level approximation, not an exact biological constant — individual results vary with water weight, muscle changes, and metabolic adaptation. This calculator uses that same logic in its TDEE examples: a 500 kcal/day deficit (3,500 kcal/week) is the standard illustration of a roughly 1 lb/week rate of loss.
How many calories should I eat to lose weight?▼
This calculator does not prescribe a calorie target — it estimates BMR, then a separate TDEE range by activity level. A commonly used starting point is eating a moderate deficit below your TDEE (not your BMR), such as the 500 kcal/day example shown in this tool’s TDEE results, which approximates a 1 lb/week rate of loss for many adults. Treat any number here as a starting estimate to monitor and adjust, not a prescription — actual needs depend on health, activity, and goals, so consult a qualified clinician or registered dietitian for individualized advice.
How many calories are in a gram of protein?▼
Protein provides 4 kcal per gram, the same Atwater factor used for carbohydrates; fat provides 9 kcal per gram. This calculator estimates total resting and daily energy needs in calories — it does not break results into grams of protein, carbs, or fat. For a gram-level breakdown of protein, carbs, and fat based on your calorie target, use the Macro Calculator.
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. pubmed.ncbi.nlm.nih.gov
- 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.
- Frankenfield DC. Bias and accuracy of resting metabolic rate equations in non-obese and obese adults. Clinical Nutrition. 2013;32(6):976–982. pubmed.ncbi.nlm.nih.gov
- National Institute of Diabetes and Digestive and Kidney Diseases. Body Weight Planner. niddk.nih.gov/bwp
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 September 9, 2026; independent professional review is pending. Next scheduled review: December 9, 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).