Utilix knowledge base
What Is BMR (Basal Metabolic Rate)?
By Utilix Editorial Team · Published Apr 17, 2026
Basal Metabolic Rate (BMR) is the number of calories your body needs to maintain basic physiological functions — breathing, circulation, cell production, and temperature regulation — while at complete rest. It represents the minimum energy expenditure required to keep you alive.
BMR accounts for roughly 60–75% of total daily energy expenditure for most sedentary people.
BMR vs TDEE
| Term | Definition |
|---|---|
| BMR | Calories burned at complete rest (no movement) |
| TDEE | Total Daily Energy Expenditure — BMR × activity multiplier |
Your TDEE is what you actually burn in a day. Eating at TDEE maintains weight; eating below it causes fat loss; eating above it causes weight gain.
How Is BMR Calculated?
Two equations are commonly used:
Mifflin-St Jeor (Recommended)
Considered the most accurate for most people:
Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
Harris-Benedict (Revised 1984)
Slightly older, still widely used:
Men: BMR = (13.397 × weight kg) + (4.799 × height cm) − (5.677 × age) + 88.362
Women: BMR = (9.247 × weight kg) + (3.098 × height cm) − (4.330 × age) + 447.593
Activity Multipliers
Multiply your BMR by the factor that best matches your lifestyle to get TDEE:
| Activity Level | Multiplier |
|---|---|
| Sedentary (desk job, little exercise) | × 1.2 |
| Lightly active (1–3 days/week exercise) | × 1.375 |
| Moderately active (3–5 days/week exercise) | × 1.55 |
| Very active (6–7 days/week hard exercise) | × 1.725 |
| Extra active (physical job + hard training) | × 1.9 |
What Affects BMR?
- Lean muscle mass — muscle burns more calories than fat at rest; higher muscle = higher BMR.
- Age — BMR typically decreases ~2% per decade after age 30.
- Sex — men generally have a higher BMR due to greater muscle mass.
- Hormones — thyroid disorders can raise (hyperthyroidism) or lower (hypothyroidism) BMR significantly.
- Diet — severe calorie restriction causes the body to reduce BMR as a survival mechanism.
Using BMR for Weight Goals
- Calculate your BMR using the BMR Calculator.
- Multiply by your activity level to get TDEE.
- Subtract 300–500 kcal/day for steady, sustainable fat loss (~0.3–0.5 kg/week).
- Add 250–500 kcal/day for gradual muscle gain.
Avoid cutting more than 1,000 kcal below TDEE — aggressive deficits cause muscle loss and metabolic adaptation.