BMR (Basal Metabolic Rate) Calculator
BMR (Basal Metabolic Rate) Calculator
Find out how many calories your body burns at rest using our BMR calculator.
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BMR: Your Body's Baseline Calorie Burn
BMR = calories burned doing absolutely nothing. If you stayed in bed all day, your body still burns energy for breathing, heartbeat, cell repair, brain function. For a 30-year-old woman, 5'5", 150 lbs: BMR = 1,450 calories. That's 60-75% of total daily burn. The rest comes from movement and digestion.
BMR differs from TDEE (Total Daily Energy Expenditure). BMR × activity multiplier = TDEE. Someone with 1,450 BMR who exercises moderately needs 2,258 total calories daily (1,450 × 1.55). Eat at BMR = lose weight. Eat at TDEE = maintain. Most people confuse these and wonder why diets fail.
BMR Calculation Methods
Mifflin-St Jeor (Most Accurate)
Men:
10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5
Women:
10 × weight(kg) + 6.25 × height(cm) - 5 × age - 161
Harris-Benedict (Original)
Men:
13.4 × weight(kg) + 4.8 × height(cm) - 5.7 × age + 88.4
Women:
9.2 × weight(kg) + 3.1 × height(cm) - 4.3 × age + 447.6
BMR to TDEE: Activity Multipliers
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Desk job, no exercise | BMR × 1.2 |
| Lightly Active | Light exercise 1-3 days/week | BMR × 1.375 |
| Moderately Active | Moderate exercise 3-5 days/week | BMR × 1.55 |
| Very Active | Hard exercise 6-7 days/week | BMR × 1.725 |
| Extra Active | Athlete, physical job + training | BMR × 1.9 |
Factors That Affect BMR
Increases BMR
- Muscle mass: +6 cal/lb muscle vs. +2 cal/lb fat
- Height: Taller = higher BMR
- Youth: Metabolism peaks at 20s
- Male sex: Men have 5-10% higher BMR
- Pregnancy/lactation: +300-500 cal/day
- Fever/illness: 7% per 1°F increase
Decreases BMR
- Aging: -1-2% per decade after 30
- Crash dieting: Adaptive thermogenesis
- Fat loss: Less mass to maintain
- Muscle loss: From inactivity/aging
- Hypothyroidism: 10-30% reduction
- Sleep deprivation: 2-5% decrease
BMR Examples by Demographics
30-Year-Old Woman
5'5" (165 cm), 150 lbs (68 kg)
BMR: 1,450 calories/day
TDEE if moderately active: 2,248 cal
30-Year-Old Man
5'10" (178 cm), 180 lbs (82 kg)
BMR: 1,850 calories/day
TDEE if moderately active: 2,868 cal
50-Year-Old Woman
5'5" (165 cm), 150 lbs (68 kg)
BMR: 1,350 calories/day
100 cal/day less than age 30
50-Year-Old Man
5'10" (178 cm), 180 lbs (82 kg)
BMR: 1,750 calories/day
100 cal/day less than age 30
How to Use Your BMR
For Weight Loss
- Never eat below BMR for extended periods (causes muscle loss)
- Calculate TDEE (BMR × activity level)
- Subtract 500 cal from TDEE for 1 lb/week loss
- Example: 1,450 BMR → 2,248 TDEE → eat 1,750 cal/day
For Muscle Gain
- Eat 250-500 cal above TDEE
- Higher protein: 0.7-1g per lb body weight
- Strength train 3-5x/week to direct surplus to muscle
For Maintenance
- Eat at your TDEE level
- Adjust every 2-3 months as weight/activity changes
- Track weekly average weight, not daily fluctuations
Frequently Asked Questions
BMR: Calories burned at complete rest (60-75% of total)
TDEE: BMR + activity + digestion = total daily burn
Weight loss: Eat between BMR and TDEE
Maintenance: Eat at TDEE
Never go below BMR long-term (muscle loss)
±10% accuracy for most people
Medical conditions (thyroid, PCOS) can change BMR by 10-30%
Yes, but modestly. Muscle burns ~6 cal/day per lb
Gaining 10 lbs muscle = +60 cal/day BMR increase
- Less muscle mass (fat burns 2 cal/lb, muscle 6 cal/lb)
- Genetics (10% variation normal)
- Thyroid issues (get checked if concerned)
- History of crash dieting (metabolic adaptation)
Yes, modestly:
- Build muscle (+60 cal per 10 lbs muscle)
- Stay hydrated (2L water = +100 cal/day)
- Get 7-9 hours sleep (sleep deprivation lowers BMR)
- Eat enough protein (higher thermic effect)
Yes. Less body mass = lower BMR (expected)
Plus adaptive thermogenesis: 5-10% extra decrease when dieting
-1-2% per decade after age 30
Mostly due to muscle loss (preventable with strength training)
Hypothyroidism: BMR 10-30% lower than predicted
Solution: Medication normalizes BMR. Work with doctor.
Yes. Metabolic testing at lab/gym ($75-150)
Measures oxygen consumption for precise number