Basal Metabolic Rate (BMR) Calculator
Know your body's true energy needs! Calculate your BMR in seconds and set smarter fitness, diet, and weight loss goals with our fast and accurate BMR Calculator.
What is BMR?
Basal Metabolic Rate (BMR) is the amount of energy (calories) your body needs while at complete rest to maintain vital functions such as breathing, circulation, and cell production.
BMR and Weight Management
Knowing your BMR is crucial for:
- Understanding your body's minimum calorie requirements
- Setting realistic weight loss or gain goals
- Developing personalized nutrition plans
- Preventing metabolic slowdown during dieting
How BMR is Calculated
This calculator uses the Mifflin-St Jeor Equation, which is considered one of the most accurate formulas for estimating BMR:
For Women: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161
Understanding TDEE
Total Daily Energy Expenditure (TDEE) is your BMR multiplied by an activity factor:
- Sedentary: BMR × 1.2 (little or no exercise)
- Lightly Active: BMR × 1.375 (light exercise 1-3 days/week)
- Moderately Active: BMR × 1.55 (moderate exercise 3-5 days/week)
- Active: BMR × 1.725 (hard exercise 6-7 days/week)
- Very Active: BMR × 1.9 (very hard exercise, physical job, or training twice a day)
What Is BMR and Why It Matters
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest just to keep you alive. It covers essential functions like breathing, circulating blood, regulating body temperature, repairing cells and keeping your brain and organs working. Even if you stayed in bed all day, you would still burn roughly this many calories.
BMR is the foundation of any calorie plan. It typically accounts for the largest share of the calories you burn each day, usually around 60-70% for most people. Knowing your BMR helps you understand a sensible baseline before you add the energy used by daily movement and exercise.
Several factors influence BMR. Body size and weight raise it, since larger bodies need more energy. Muscle mass burns more calories than fat at rest. Age tends to lower BMR over time, and sex matters because men generally carry more muscle. This is why a good formula uses weight, height, age and sex together.
The Mifflin-St Jeor Equation
This calculator uses the Mifflin-St Jeor equation, widely regarded as one of the most accurate BMR formulas for the general population. It requires weight in kilograms, height in centimetres and age in years.
- Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
- Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
Worked example (man): a 30-year-old man weighing 80 kg at 178 cm tall. BMR = (10 × 80) + (6.25 × 178) − (5 × 30) + 5 = 800 + 1112.5 − 150 + 5 = 1767.5 calories per day.
Worked example (woman): a 30-year-old woman weighing 65 kg at 165 cm tall. BMR = (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 650 + 1031.25 − 150 − 161 = 1370.25 calories per day.
If you only have your weight in pounds or height in inches, convert first: 1 kg = 2.205 lb and 1 inch = 2.54 cm.
From BMR to TDEE Using Activity Multipliers
Your BMR is calories at rest, but you also move, work and exercise. Total Daily Energy Expenditure (TDEE) is your full daily calorie burn. To estimate it, multiply your BMR by an activity factor that reflects how active you are.
| Activity level | Multiplier |
| Sedentary (little or no exercise) | 1.2 |
| Lightly active (1-3 days/week) | 1.375 |
| Moderately active (3-5 days/week) | 1.55 |
| Very active (6-7 days/week) | 1.725 |
| Extra active (hard exercise or physical job) | 1.9 |
Example: using the man above with a BMR of 1767.5, a moderately active lifestyle gives TDEE = 1767.5 × 1.55 = about 2740 calories per day. That figure is roughly the amount he needs to maintain his current weight.
Using Your Numbers Sensibly
Once you know your TDEE, you can plan around it. To maintain weight, eat close to your TDEE. To lose weight, eat in a moderate deficit, often 300-500 calories below TDEE, which targets a gradual loss. To gain weight or muscle, eat a modest surplus above TDEE alongside resistance training.
Remember these formulas give estimates, not exact values. Real energy needs vary with genetics, body composition, hormones and how accurately you log food and activity. Treat the result as a starting point and adjust based on real-world results over a few weeks.
This tool is for general information only. If you have a medical condition, are pregnant, or are planning a significant change to your diet or exercise, consult a doctor or registered dietitian before acting on these numbers.
Frequently Asked Questions
BMR is the calories your body burns at complete rest for basic functions. TDEE is your total daily calorie burn, which includes BMR plus the energy used for movement, exercise and digestion. You calculate TDEE by multiplying BMR by an activity factor.
It is considered one of the most reliable BMR formulas for the general public and tends to be more accurate than older equations like Harris-Benedict. It is still an estimate, as it cannot account for individual differences in body composition, so use the result as a guide.
No. The Mifflin-St Jeor equation only needs your weight, height, age and sex. Formulas such as the Katch-McArdle equation use lean body mass instead, which requires a known body fat percentage, but that is a separate method.
On average men carry more muscle and less body fat than women of the same size, and muscle burns more energy at rest. The equation reflects this with a different constant, adding 5 for men and subtracting 161 for women.
Generally no. Eating at or below your BMR for long periods can be too aggressive and hard to sustain. A common approach is to eat in a moderate deficit below your TDEE rather than your BMR. Speak with a healthcare professional or dietitian for a plan suited to you.
Recalculate whenever your weight changes noticeably, or every few months, since BMR shifts with weight and age. Updating your numbers keeps your calorie targets realistic as your body changes.