Health Calculator

BMR & TDEE Calculator

Calculate your Basal Metabolic Rate and Total Daily Energy Expenditure using three validated formulas simultaneously, Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle. Includes activity multipliers, goal calorie targets, and macronutrient breakdown.

3 validated formulas Instant results PDF & CSV export
BMR / TDEE Calculator
yrs
Please enter a valid age (15–100).
kg
Please enter a valid weight.
cm
Please enter a valid height (100–250 cm).
%
Leave blank to use estimated lean body mass instead.
Your Results
-
kcal / day to maintain current weight

BMR by formula (calories/day at complete rest):

Mifflin-St Jeor
-
kcal/day
Most Accurate
Harris-Benedict
-
kcal/day
Katch-McArdle
-
kcal/day

Daily calorie targets by goal:

Lose Weight
-
500 kcal deficit
~0.5 kg/week
Maintain
-
Current TDEE
No change
Gain Muscle
-
300 kcal surplus
Lean bulk

Estimated macronutrient targets (maintenance):

🍗 Protein -
🌾 Carbohydrates -
🥑 Fat -

What Is Basal Metabolic Rate (BMR)?

Basal Metabolic Rate is the minimum number of calories your body requires to sustain essential physiological functions at complete rest, breathing, heartbeat, cell repair, temperature regulation, and organ function. BMR accounts for approximately 60–70% of total daily energy expenditure in sedentary individuals and decreases with age as lean muscle mass naturally declines. It also rises substantially during pregnancy to support fetal growth and increased maternal blood volume, a period-specific shift that general BMR formulas do not capture, so pregnant users should instead consult our Pregnancy BMI and Weight Gain Calculator.

The Three BMR Formulas

FormulaYearBest ForError Range
Mifflin-St Jeor1990Most non-obese adults±10%
Harris-Benedict (revised)1984General population±12%
Katch-McArdle1996Athletes with known lean mass±5% (when BF% known)

All three formulas treat body weight as their dominant variable, the same measurement that underlies other clinical calculations such as weight-based medication dosing, which is why an accurate scale reading matters as much as the formula you choose.

Activity Multipliers (Harris-Benedict)

These multipliers approximate weekly exercise volume rather than prescribe it. For baseline guidance on how much movement adults need independent of any BMR calculation, the CDC Physical Activity Guidelines for Americans recommend at least 150 minutes of moderate-intensity activity per week.

LevelMultiplierDescription
Sedentary× 1.2Desk job, minimal movement
Lightly Active× 1.375Light exercise 1–3 days/week
Moderately Active× 1.55Exercise 3–5 days/week
Very Active× 1.725Hard exercise 6–7 days/week
Extremely Active× 1.9Physical job + daily training

Macronutrient Distribution

The macronutrient targets shown fall within the Acceptable Macronutrient Distribution Ranges set by the National Institutes of Health Office of Dietary Supplements: protein 10–35%, carbohydrates 45–65%, and fat 20–35% of total calories. These are general starting points, individual needs vary significantly by goal, medical condition, and dietary preference.

Frequently Asked Questions

What is the difference between BMR and TDEE?+
BMR is the calories burned at complete rest, if you did nothing but lie in bed all day. TDEE (Total Daily Energy Expenditure) adds the energy cost of all daily activity, exercise, and the thermic effect of food. TDEE is the number you actually need to consume to maintain your weight. Eating below TDEE causes weight loss; eating above causes gain.
Why does my BMR decrease with age?+
BMR decreases with age primarily because of the gradual loss of lean muscle mass (sarcopenia) that begins in the third decade of life. Muscle tissue is metabolically active and burns more calories at rest than fat tissue. Also, hormonal changes (declining testosterone, growth hormone, and thyroid function) contribute to reduced resting metabolism. Resistance training can partially offset age-related BMR decline.
How many calories should I eat to lose 1 kg per week?+
One kilogram of fat contains approximately 7,700 kcal. To lose 1 kg per week, you would need a daily calorie deficit of approximately 1,100 kcal (7,700 ÷ 7). Most guidelines recommend a maximum deficit of 500–750 kcal/day (0.5 kg/week) for sustainable, safe weight loss. Larger deficits risk muscle loss, nutrient deficiencies, and metabolic adaptation. Always consult a dietitian for personalised advice.
Is Katch-McArdle more accurate than Mifflin-St Jeor?+
For athletes and individuals with known body fat percentage, yes, Katch-McArdle can be more accurate because it calculates BMR from lean body mass directly, bypassing the height/weight/age approximation. However, if body fat percentage is estimated (not measured), the error introduced negates the formula's advantage. For most people without DEXA or caliper measurements, Mifflin-St Jeor remains the recommended choice.

Related Tools

Use BMR alongside Caloric Needs Calculator for detailed macronutrient planning, BMI Calculator for weight classification, and Body Fat Percentage for lean mass estimation to use with Katch-McArdle.

References

  • Mifflin MD, et al. "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr. 1990;51(2):241-247.
  • Harris JA, Benedict FG. A Biometric Study of Human Basal Metabolism. Carnegie Institution, 1919. (Revised Roza & Shizgal, 1984.)
  • Katch V, McArdle W. Nutrition, Weight Control, and Exercise. 3rd ed. Lea & Febiger, 1988.
  • Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. NAP, 2005.
⚠️ Medical Disclaimer: BMR and TDEE estimates have an inherent margin of error of ±10–20%. These are general reference values. For clinical nutrition support, medical weight management, or eating disorder recovery, always work with a registered dietitian or physician.