How Daily Calorie Needs Are Calculated
Your Total Daily Energy Expenditure (TDEE) is the number of calories your body burns in a day, accounting for your basal metabolic rate (BMR) — the energy needed just to stay alive — plus the calories burned through physical activity. The Mifflin-St Jeor equation, developed in 1990, is the most accurate formula for estimating BMR and is used by most registered dietitians today.
Worked Example
A 35-year-old woman, 5'5" (165 cm), 140 lbs (63.5 kg), moderately active: BMR = (10 × 63.5) + (6.25 × 165) − (5 × 35) − 161 = 635 + 1031.25 − 175 − 161 = 1,330 calories/day. Multiply by the moderate activity factor (1.55): TDEE = 1,330 × 1.55 = 2,062 calories/day. To lose 1 lb per week, she would eat 2,062 − 500 = 1,562 calories/day.
Activity Multipliers (Mifflin-St Jeor)
| Activity Level | Multiplier | Description |
|---|
| Sedentary | 1.2 | Desk job, little or no exercise |
| Lightly active | 1.375 | Light exercise 1–3 days/week |
| Moderately active | 1.55 | Moderate exercise 3–5 days/week |
| Very active | 1.725 | Hard exercise 6–7 days/week |
| Extra active | 1.9 | Physical job + hard daily exercise |
How daily calorie needs are calculated
The most widely used formula is the Mifflin-St Jeor equation, which estimates Basal Metabolic Rate (BMR) — the calories your body burns at rest. BMR is then multiplied by an activity factor to get Total Daily Energy Expenditure (TDEE). For weight loss, eat 500 kcal below TDEE; for weight gain, eat 500 kcal above.
Worked example (male, 30 years, 80 kg, 178 cm, moderately active): BMR = (10 × 80) + (6.25 × 178) − (5 × 30) + 5 = 800 + 1112.5 − 150 + 5 = 1767.5 kcal. TDEE = 1767.5 × 1.55 = 2,740 kcal/day.
| Activity Level | Multiplier |
|---|
| Sedentary (desk job, no exercise) | × 1.2 |
| Lightly active (1–3 days/week) | × 1.375 |
| Moderately active (3–5 days/week) | × 1.55 |
| Very active (6–7 days/week) | × 1.725 |
| Extra active (physical job + training) | × 1.9 |
