BMR calculator guide (Mifflin–St Jeor) + how to use it for goals
BMR is your baseline calorie burn at rest. Use BMR to estimate TDEE (maintenance calories), then plan a sustainable deficit or surplus based on your goal.
How We Calculate It: The Mifflin-St Jeor Formula
We use the Mifflin-St Jeor Equation, considered the "gold standard" for accuracy in 2026. It is more reliable than the older Harris-Benedict formula.
Men: (10 Ă— weight_kg) + (6.25 Ă— height_cm) - (5 Ă— age_years) + 5
Women: (10 Ă— weight_kg) + (6.25 Ă— height_cm) - (5 Ă— age_years) - 161
*Note: This gives you your BMR (calories burned at complete rest). To get your real daily burn (TDEE), we multiply this by an "Activity Factor".
Glossary of Key Metabolic Terms
Understanding these 6 specialized terms is crucial for mastering your metabolism:
| Term | Definition | Why It Matters |
|---|---|---|
| BMR (Basal Metabolic Rate) | Calories burned at *complete* rest (coma-like state) to keep organs alive. | Your absolute minimum energy floor. |
| RMR (Resting Metabolic Rate) | Calories burned at rest but with minimal movement (sitting, digesting). | Often used interchangeably with BMR, but usually ~10% higher. |
| TDEE (Total Daily Energy Expenditure) | Your BMR + Activity + Digestion. The total calories you burn in a day. | Use THIS number, not BMR, to calculate calorie deficits. |
| NEAT (Non-Exercise Activity Thermogenesis) | Calories burned from fidgeting, walking, standing, and daily tasks. | Can vary by 500+ calories/day between people. A major hidden fat-loss tool. |
| TEF (Thermic Effect of Food) | Calories burned digesting food (Protein has high TEF, Fat has low). | Eating more protein boosts your metabolism slightly via TEF. |
| Metabolic Adaptation | The body slowing down BMR in response to weight loss to 'survive'. | The reason why weight loss plateaus happen and why 'crash diets' fail long-term. |
BMR vs. RMR: What's the Difference?
- Clinical Strictness: BMR effectively requires overnight fasting in a dark room immediately upon waking. RMR is more relaxed (sitting quietly).
- Real World: For most people, the difference is negligible impacting daily goals by less than 100 calories. Our calculator estimates BMR but effectively serves as a baseline for RMR planning.
How to turn BMR into a goal plan
| Goal | Target Calories (Daily) | Strategy |
|---|---|---|
| Fat Loss | TDEE - 500 | Creates ~1lb/week loss. Don't eat below BMR long-term. |
| Maintenance | Equal to TDEE | Monitor weekly average weight. |
| Muscle Gain | TDEE + 250 | Minimize fat gain while fueling muscle growth. |
Can you actually 'boost' your metabolism?
Yes, but "fat burner pills" don't work. The only proven ways to increase BMR/TDEE are:
- Build Muscle: Muscle tissue burns ~3x more calories at rest than fat tissue.
- Increase NEAT: Walk more, stand while working, take stairs.
- Eat Protein: High TEF means you burn 20-30% of protein calories just digesting them.
BMR FAQ
Q:What is BMR?
BMR (Basal Metabolic Rate) is the estimated calories your body burns at rest to support vital functions like breathing, circulation, and organ function. It’s a baseline used to estimate daily calorie needs.
Q:What’s the difference between BMR and TDEE?
BMR is calories at rest. TDEE (Total Daily Energy Expenditure) includes BMR plus daily activity, exercise, and the thermic effect of food. TDEE is the better number to plan weight loss, maintenance, or muscle gain calories.
Q:What formula does this calculator use?
This calculator uses the Mifflin–St Jeor equation, a widely used and validated method for estimating resting energy expenditure.
Q:How accurate is BMR?
BMR equations are estimates. Individual metabolism varies due to body composition, hormones, genetics, and health conditions. Use BMR/TDEE as a starting point and adjust based on real-world weight trends and energy levels.