BMR & TDEE Calculator
Basal Metabolic Rate • Daily Calorie Needs
What Is BMR (Basal Metabolic Rate)?
BMR (Basal Metabolic Rate) is the number of calories your body needs to perform its most basic life-sustaining functions — breathing, circulating blood, regulating body temperature, cell repair, and brain function — while at complete rest. Think of it as the minimum fuel your body requires to keep the engine running if you stayed in bed all day.
How This BMR Calculator Works
This calculator uses the Mifflin-St Jeor Equation, widely regarded as the most accurate BMR formula by the Academy of Nutrition and Dietetics. It was developed in 1990 and has been validated in numerous scientific studies for its precision across diverse populations.
The Mifflin-St Jeor Formula:
- For Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- For Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
The calculator then multiplies your BMR by an activity factor to estimate your TDEE (Total Daily Energy Expenditure) — the total calories you burn each day including all physical activity.
What Is TDEE?
TDEE (Total Daily Energy Expenditure) is your BMR plus all additional calories burned through daily activities, exercise, and the thermic effect of food (digestion). It represents your total calorie burn in a 24-hour period and is the number you need to know for weight management.
Activity Level Multipliers:
- Sedentary (×1.2): Desk job, little to no exercise
- Lightly Active (×1.375): Light exercise or sports 1–3 days per week
- Moderately Active (×1.55): Moderate exercise or sports 3–5 days per week
- Very Active (×1.725): Hard exercise or sports 6–7 days per week
- Extra Active (×1.9): Very hard daily exercise, physical labor job, or training twice per day
How to Use BMR & TDEE for Weight Management
Once you know your TDEE, you can adjust your calorie intake to achieve your goals:
- Weight Loss: Eat 300–500 calories below your TDEE. This creates a sustainable deficit leading to roughly 0.5–1 lb of fat loss per week.
- Weight Maintenance: Eat approximately equal to your TDEE to maintain your current weight.
- Weight Gain / Muscle Building: Eat 300–500 calories above your TDEE, combined with strength training, to support muscle growth.
Factors That Influence Your BMR
Several factors affect your basal metabolic rate beyond the numbers you enter into the calculator:
- Age: BMR naturally decreases with age, primarily due to loss of muscle mass
- Muscle Mass: More muscle = higher BMR. Muscle tissue burns more calories at rest than fat tissue
- Genetics: Some people are born with a naturally faster or slower metabolism
- Hormones: Thyroid hormones, stress hormones, and sex hormones all influence metabolic rate
- Body Size: Larger bodies generally have a higher BMR due to more metabolically active tissue
- Climate & Temperature: Living in extreme cold or heat can increase BMR
- Diet & Nutrition: Severe calorie restriction can lower BMR as the body adapts to conserve energy
Frequently Asked Questions
🤔 How accurate is the BMR calculator?
The Mifflin-St Jeor equation is considered the most accurate for the general population, with an error margin of about ±10% for most individuals. However, individual variations in body composition (muscle vs. fat ratio) can affect accuracy. For the most precise measurement, a lab-based indirect calorimetry test is required.
📊 Should I use BMR or TDEE for weight loss?
Use your TDEE as the baseline for weight loss calculations. Subtract 300–500 calories from your TDEE (not your BMR) to create a healthy calorie deficit. Using BMR as your baseline would result in too aggressive a deficit.
🔄 How often should I recalculate my BMR?
Recalculate your BMR whenever your weight changes by 10 lbs (4–5 kg) or more, or after significant changes in body composition. It's also wise to recalculate every 6–12 months as age incrementally affects your BMR.
🏋️ Does exercise increase BMR?
Yes — regular exercise, especially strength training, builds muscle mass which raises your BMR over time. Even at rest, muscle tissue burns more calories than fat tissue. Cardiovascular exercise also provides a temporary metabolic boost after workouts (the "afterburn" effect or EPOC).
🍽️ Can dieting lower my BMR?
Yes. Prolonged severe calorie restriction can cause adaptive thermogenesis — your body slows its metabolism to conserve energy. This is why many people experience weight loss plateaus. Incorporating diet breaks and avoiding extreme deficits helps mitigate this effect.
Disclaimer: This calculator provides estimates for educational purposes only. It is not a substitute for professional medical or nutritional advice. Always consult with a qualified healthcare provider for personalized guidance.
