Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns in 24 hours — accounting for everything from keeping your heart beating while you sleep to a CrossFit class. Understanding your TDEE is the single most important number in nutrition, because it tells you exactly how much to eat to maintain, lose, or gain weight.
The Components of TDEE
TDEE is made up of four components:
- Basal Metabolic Rate (BMR) — 60–75% of TDEE
The calories burned at complete rest — just to keep you alive. This covers organ function, cell repair, breathing, and body temperature regulation. BMR is primarily driven by body mass, muscle mass, age, and sex. - Thermic Effect of Activity (TEA) — 15–30%
Calories burned during deliberate exercise: gym sessions, sports, cycling to work. - Non-Exercise Activity Thermogenesis (NEAT) — 5–15%
Calories from all movement that isn't formal exercise: fidgeting, walking around the office, doing the washing up. This varies enormously between individuals and explains why two people with the same BMR can have very different TDEEs. - Thermic Effect of Food (TEF) — ~10%
Calories burned digesting and processing food. Protein has the highest TEF (~20–30%), followed by carbohydrates (~5–10%) and fat (~0–3%).
The Mifflin-St Jeor Equation (Most Accurate BMR Formula)
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: 35-year-old woman, 65 kg, 165 cm
BMR = (10 × 65) + (6.25 × 165) − (5 × 35) − 161
= 650 + 1031.25 − 175 − 161
= 1,345 calories/day
Activity Multipliers (TDEE = BMR × Activity Factor)
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Desk job, little exercise | × 1.2 |
| Lightly active | Light exercise 1–3 days/week | × 1.375 |
| Moderately active | Moderate exercise 3–5 days/week | × 1.55 |
| Very active | Hard exercise 6–7 days/week | × 1.725 |
| Extremely active | Physical job + daily training | × 1.9 |
For our example woman (lightly active): TDEE = 1,345 × 1.375 = 1,850 calories/day
Setting Calorie Targets
Weight Loss
A deficit of 500 calories/day below TDEE produces approximately 0.5 kg (1 lb) of fat loss per week. This is the sustainable, evidence-based target. Larger deficits (800–1,000 cal/day) can work short-term but risk muscle loss, nutrient deficiency, and metabolic adaptation ("starvation mode").
Minimum intake recommendations: 1,200 cal/day for women, 1,500 cal/day for men — never go below these without medical supervision.
Muscle Gain (Bulking)
A surplus of 200–300 cal/day above TDEE, combined with progressive resistance training, supports lean muscle gain. Larger surpluses lead to proportionally more fat gain. A slow bulk of 0.5 kg/month is preferable to gaining fat rapidly.
Body Recomposition
Eating at approximately TDEE while resistance training can simultaneously reduce fat and build muscle — especially effective for beginners or those returning after a break. Progress is slower but more sustainable, and body composition improves even without weight change on the scales.
Why Calorie Calculators Are Estimates
No formula can account for individual metabolic variation. Studies show TDEE calculations can be off by ±200–300 calories even with perfect inputs. Factors that introduce error include:
- Gut microbiome efficiency (how many calories you actually absorb vs what's on the label)
- Sleep quality (poor sleep increases hunger hormones — ghrelin — and reduces satiety hormones — leptin)
- Stress and cortisol levels
- Thyroid function
- Medication effects
Use your calculated TDEE as a starting point, then track your weight for 2–3 weeks. If weight isn't changing as expected, adjust intake by 100–150 calories and reassess.
Macronutrient Targets
Once you have your calorie target, split it into macronutrients:
- Protein: 1.6–2.2 g per kg bodyweight (essential for muscle preservation during a deficit)
- Fat: Minimum 20% of total calories for hormone health
- Carbohydrates: Remaining calories — the most flexible macro
For our 65 kg woman at 1,350 cal/day (500 below TDEE): Protein = 65 × 1.8 = 117 g (468 cal), Fat = 1350 × 0.25 = 338 cal = 37.5 g, Carbs = (1350 − 468 − 338) ÷ 4 = 136 g.
Summary
Calculate your BMR using the Mifflin-St Jeor equation, then multiply by your activity factor to get TDEE. For weight loss, eat 300–500 calories below TDEE. For muscle gain, eat 200–300 above. Treat the calculator result as an estimate and adjust based on real-world weight trend data over 2–3 weeks.