Step 1: Calculate your BMR
BMR (Basal Metabolic Rate, basal metabolism) is the calories your body burns at complete rest — only to keep the heart, brain and organs running. It is the foundation for all calorie calculations.
The most widely used and validated formula for most adults is Mifflin-St Jeor: Mifflin-St Jeor:
- Men: BMR = (9.99 × weight) + (6.25 × height) − (4.92 × age) + 5
- Women: BMR = (9.99 × weight) + (6.25 × height) − (4.92 × age) − 161
Weight in kg, height in cm, age in years.
Step 2: Calculate your TDEE with activity factor
TDEE (Total Daily Energy Expenditure) is your total calorie need — BMR multiplied by your PAL factor (Physical Activity Level).
| Level | Description | PAL factor |
|---|---|---|
| Sedentary | Office or home work, little daily movement, no training | 1.2 |
| Lightly active | Light exercise 1–3 days/week, e.g. walks, yoga or gym in spare time | 1.375 |
| Moderately active | Regular exercise 3–5 days/week with moderate intensity, e.g. running or strength training | 1.55 |
| Very active | Hard training almost every day (6–7 days/week) or physically active work | 1.725 |
| Extremely active | Heavy physical work combined with daily intense training, e.g. elite athletes or construction workers who also train | 1.9 |
Example: A person, 30 years old, 80 kg, 180 cm, trains 3–5 times/week (moderately active).
BMR = (9.99 × 80) + (6.25 × 180) − (4.92 × 30) + 5 = 1,895 kcal
TDEE = 1,895 × 1.55 = 2,937 kcal/day
Step 3: Adjust for your goal
Weight loss (cut)
Eat 300–500 kcal below your TDEE. That gives about 0.3–0.5 kg of weight loss per week — slow enough to preserve muscle mass. Combine with adequate protein (1.6–2.2 g/kg) for best results.
Muscle building (bulk)
Eat 200–400 kcal above your TDEE. That creates a small surplus for muscle growth with minimal fat gain. More than 500 kcal/day in surplus often leads to unnecessary fat storage.
Maintenance
Match your TDEE. Great during rest periods, rehabilitation or to stabilise weight after a longer phase.
Why doesn't the calculator always match?
TDEE calculators provide an estimate with a margin of error of typically ±10–15%. Factors that affect the real value:
- Muscle mass (more muscle = higher BMR)
- Thyroid hormones and other hormonal balance
- Sleep quality
- Thermic effect of food (proteins require more energy to digest)
- Adaptive thermogenesis (body lowers metabolism during prolonged calorie deficit)
Practical tip: Use the calculator as a starting point. Monitor your weight for 2–3 weeks and adjust the calorie goal if you don't see the expected result.