Basal Metabolic Rate (BMR)
Your BMR is the number of calories your body burns at complete rest — the baseline all calorie planning starts from.
Peer-Reviewed Formulas
All three equations are published in peer-reviewed journals — no guesswork, no black-box algorithms.
Not Medical Advice
BMR estimates are statistical averages. Consult a registered dietitian for personalised nutrition plans.
What is Basal Metabolic Rate (BMR)?
The minimum calories your body needs to stay alive
Your Basal Metabolic Rate (BMR) is the number of kilocalories your body burns every day to maintain basic physiological functions — breathing, heartbeat, cell repair, body temperature — while you are completely at rest. It accounts for roughly 60–75 % of your total daily energy expenditure in a sedentary person.
Quick Answer: BMR is your "idle" calorie burn. Multiply it by your activity level to get your Total Daily Energy Expenditure (TDEE) — the actual number of calories you need to maintain your current weight.
Three equations dominate clinical and research use. All three produce values in kcal/day — the number of kilocalories your body burns at rest in 24 hours.
Mifflin-St Jeor (1990) — Recommended
The most widely validated equation for healthy adults, developed from a sample of 498 adults and cross-validated in multiple subsequent studies.
BMR = 10 × kg + 6.25 × cm − 5 × age + Swhere S = +5 for males and S = −161 for females.
Revised Harris-Benedict (1984)
The original Harris-Benedict equation dates to 1919. Roza and Shizgal revised the coefficients in 1984 using more accurate body composition data. It is still widely cited in clinical settings.
BMR = 88.362 + 13.397 × kg + 4.799 × cm − 5.677 × ageBMR = 447.593 + 9.247 × kg + 3.098 × cm − 4.330 × ageKatch-McArdle
Unique in that it uses lean body mass (LBM) rather than total weight and ignores sex entirely. This makes it the most accurate formula when you know your body fat percentage — athletes, people with high muscle mass, or anyone with a body composition measurement.
BMR = 370 + 21.6 × LBM where LBM = kg × (1 − bodyFat/100)Use Mifflin-St Jeor
You do not know your body fat %. You want the single best validated estimate for average healthy adults. Most clinical guidelines default to this equation.
Use Harris-Benedict
Your healthcare provider or dietitian specifically requests the Harris-Benedict estimate. It produces slightly higher values than Mifflin for most people.
Use Katch-McArdle
You have a measured body fat percentage (DEXA, hydrostatic weighing, calibrated calipers). Athletes and highly muscular individuals get the most accurate result from this formula.
Research consensus: A 2005 review in the Journal of the American Dietetic Association found that Mifflin-St Jeor predicts resting energy expenditure within 10% for approximately 82% of non-obese individuals — the highest accuracy of the four most commonly used equations.
Your BMR is your floor — the calories you burn doing nothing. To find how many calories you actually need per day, multiply your BMR by your Physical Activity Level (PAL) multiplier.
| Activity Level | Multiplier | Description | Example TDEE (BMR = 1,780) |
|---|---|---|---|
| Sedentary | × 1.2 | Desk job, little or no exercise | 2,136 kcal |
| Lightly active | × 1.375 | Light exercise 1–3 days/week | 2,448 kcal |
| Moderately active | × 1.55 | Moderate exercise 3–5 days/week | 2,759 kcal |
| Very active | × 1.725 | Hard exercise 6–7 days/week | 3,070 kcal |
| Extra active | × 1.9 | Very hard exercise or physical job | 3,382 kcal |
These multipliers are derived from the FAO/WHO/UNU Human Energy Requirements report (2004), which synthesised data from doubly labelled water studies across multiple populations.
Choosing your activity level: Most people overestimate their activity. Choose the level that describes your average week — not your best week. Sedentary or lightly active covers the majority of desk workers, even those who go to the gym 2–3 times per week.
BMR is not how many calories you should eat — it is the minimum your body needs to survive at complete rest. Eating at or below your BMR is a form of severe calorie restriction that can cause muscle loss, hormonal disruption, and metabolic adaptation.
Weight maintenance
Eat at TDEE (BMR × activity multiplier) to maintain your current weight. Your TDEE is displayed alongside your BMR in the calculator result.
Weight loss
A deficit of 500 kcal/day below TDEE produces roughly 0.5 kg per week of weight loss. Most dietitians recommend not going below BMR.
BMR vs TDEE — The Key Distinction
BMR is what your body burns in bed, doing nothing. TDEE (Total Daily Energy Expenditure) is what you actually burn in your daily life. The calculator shows both — BMR is the foundation, TDEE is the planning number.
BMR formulas are population averages derived from regression analysis. Individual BMR can vary by ±10–15% from any formula's estimate due to genetics, body composition, thyroid function, medication, and other factors.
This calculator provides estimates only
BMR equations were derived from healthy adults and may be less accurate for people with thyroid disorders, metabolic conditions, obesity class III, or those who have experienced significant weight loss. The estimates do not replace metabolic testing (indirect calorimetry) for clinical nutrition planning. Always consult a registered dietitian or physician before making significant changes to your calorie intake.