Basal Metabolic Rate (BMR) Calculator
Basal Metabolic Rate (BMR) is the number of calories your body needs to perform basic life-sustaining functions while at complete rest. These functions include breathing, blood circulation, cell production, nutrient processing, and maintaining body temperature. BMR accounts for roughly 60–75% of your total daily calorie expenditure.
BMR varies between individuals based on age, weight, height, gender, and body composition. As you age, your BMR typically decreases due to loss of muscle mass. Understanding your BMR is the foundation for creating effective nutrition plans, whether your goal is weight loss, muscle gain, or maintenance. Combined with an activity factor, BMR helps calculate your Total Daily Energy Expenditure (TDEE).
How it works
Mifflin-St Jeor equation: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age in years) + s, where s is +5 for males and −161 for females. This is considered the most accurate BMR formula for most people.
Use cases
- Establishing a calorie baseline for weight loss or gain plans
- Understanding your minimum daily caloric needs
- Comparing metabolic rates before and after fitness programs
- Supporting clinical nutrition assessments and dietary planning
Frequently asked questions
What is basal metabolic rate (BMR)?
BMR is the number of calories your body burns at complete rest just to keep vital functions running — breathing, circulation, cell production, and temperature regulation. It accounts for roughly 60–75% of the total calories most people burn in a day. Everything else comes from physical activity and digesting food.
How is BMR calculated?
This calculator uses the Mifflin-St Jeor equation: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + s, where s is +5 for males and −161 for females. For example, a 30-year-old man weighing 80 kg at 180 cm has a BMR of 800 + 1125 − 150 + 5 = 1780 kcal per day. This equation is considered the most accurate for most people.
What is the difference between BMR and TDEE?
BMR covers only the calories burned at complete rest, while TDEE (Total Daily Energy Expenditure) adds the energy used in daily activity and digestion. TDEE is estimated by multiplying BMR by an activity factor from 1.2 (sedentary) to 1.9 (extremely active). Calorie targets for weight loss or gain should be based on TDEE, not BMR alone.
Should I eat fewer calories than my BMR to lose weight?
Weight loss requires eating below your TDEE, not necessarily below your BMR. Consistently eating far below BMR can lead to muscle loss, nutrient deficiencies, and metabolic slowdown. Before starting a restrictive diet, consult a registered dietitian or physician to set a safe calorie target for your situation.
Why does BMR decrease with age?
BMR declines mainly because of the gradual loss of muscle mass that comes with aging, since muscle tissue burns more calories at rest than fat tissue. The Mifflin-St Jeor equation reflects this by subtracting 5 kcal for each year of age. Strength training helps preserve muscle mass and slow this decline.