Whether you want to lose weight, gain muscle, or simply maintain your current body weight, the starting point for any conscious diet is knowing your BMR (Basal Metabolic Rate) and TDEE (Total Daily Energy Expenditure). Without these values, dieting or bulking is little more than guesswork.
What Is BMR?
BMR (Basal Metabolic Rate) is the number of calories your body burns in 24 hours at complete rest — purely to sustain basic life functions: heartbeat, breathing, kidney function, and thermoregulation. BMR does not account for any physical activity.
The most widely used formula is Mifflin-St Jeor, the standard recommended by dietitians in 2026:
- Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
- Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161
Example: Woman, 30 years old, 65 kg, 168 cm → BMR = 650 + 1,050 − 150 − 161 = 1,389 kcal/day.
What Is TDEE and How to Calculate It?
TDEE (Total Daily Energy Expenditure) is the total number of calories burned throughout the day, accounting for your physical activity level. It is calculated by multiplying BMR by an activity multiplier (PAL):
- Sedentary (desk job, no exercise): × 1.2
- Lightly active (1–3 workouts/week): × 1.375
- Moderately active (3–5 workouts/week): × 1.55
- Very active (6–7 workouts/week): × 1.725
- Extra active (physical job + training): × 1.9
For the woman in our example, with moderate activity: TDEE = 1,389 × 1.55 = 2,153 kcal/day.
How to Use TDEE to Change Your Weight
Once you know your TDEE, you can plan your diet:
- Maintain weight: eat as many calories as your TDEE.
- Lose weight: eat 300–500 kcal fewer than TDEE. A 500 kcal/day deficit equals roughly 0.5 kg of weight loss per week. Never go below your BMR!
- Build muscle: eat 200–400 kcal more than TDEE (a controlled surplus) to minimise fat gain.
BMR, Age and Sex — Why It Matters
BMR naturally declines with age — by approximately 1–2% per decade after the age of 30. Men have a higher BMR than women of the same weight and height because they carry more metabolically active muscle tissue. This is why dietary calorie targets should always be individually tailored.
Use the BMR Calculator
Instead of calculating by hand, use the BMR and TDEE calculator on Liczbnik. Simply enter your sex, age, weight, height, and activity level — the tool instantly shows your BMR, TDEE, and recommended calorie intake for different goals (weight loss, maintenance, muscle gain).
Summary
BMR is the minimum number of calories you need to stay alive, while TDEE is your actual daily requirement including activity. Knowing both figures allows you to plan a diet precisely matched to your goals — without starvation and without the yo-yo effect.