If you've ever followed a calorie target that didn't work — eating 1,500 kcal and not losing weight, or eating 3,000 and not gaining muscle — the problem was probably your TDEE estimate.
TDEE stands for Total Daily Energy Expenditure: the number of calories your body burns in a 24-hour period. Get it right and weight management becomes a predictable equation. Get it wrong and you're either starving or over-eating without knowing it.
What Is TDEE?
Your TDEE is made up of four components:
- Basal Metabolic Rate (BMR) — calories burned at complete rest, just to keep you alive. This accounts for roughly 60–75% of total expenditure for most people.
- Thermic Effect of Activity (TEA) — calories burned during deliberate exercise.
- Non-Exercise Activity Thermogenesis (NEAT) — calories burned through all movement that isn't structured exercise: walking, fidgeting, standing, typing. This is highly variable and accounts for 15–30% of TDEE.
- Thermic Effect of Food (TEF) — calories burned digesting food. About 10% of total intake.
Most diet advice focuses on TEA (your workouts), but NEAT is often the more powerful lever — and the one most affected by calorie restriction.
The Mifflin-St Jeor Formula
The most accurate formula for estimating BMR without lab equipment is the Mifflin-St Jeor equation:
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
Once you have your BMR, multiply by your activity multiplier to get TDEE:
| Activity Level | Multiplier | What It Means |
|---|---|---|
| Sedentary | 1.2 | Desk job, no exercise |
| Lightly active | 1.375 | 1–3 workouts per week |
| Moderately active | 1.55 | 3–5 workouts per week |
| Very active | 1.725 | Hard training 6–7 days/week |
| Extra active | 1.9 | Physical job + daily training |
Example: A 35-year-old woman, 165 cm, 75 kg, moderately active: BMR = (10 × 75) + (6.25 × 165) − (5 × 35) − 161 = 1,496 kcal TDEE = 1,496 × 1.55 = 2,319 kcal/day
Why TDEE Estimates Are Often Wrong
The formula gives you a starting point — not a guaranteed number. Three things throw it off:
1. Metabolic adaptation. Sustained calorie restriction reduces BMRR by 10–20% over months. Your calculated TDEE assumes no adaptation. After 3+ months of dieting, your actual TDEE may be significantly lower.
2. Activity overestimation. Most people select "moderately active" when they go to the gym 3 times per week — but if they sit at a desk the rest of the time, "lightly active" is more accurate. Overestimating activity by just one level adds ~200–300 kcal to your target.
3. NEAT suppression. When you cut calories, your brain unconsciously reduces NEAT. You fidget less, take fewer steps, move less efficiently. Studies show NEAT can drop by 200–700 kcal/day during aggressive cuts — which means your actual TDEE drops even if your workouts stay constant.
How to Calibrate Your Real TDEE
The most reliable method is empirical calibration:
- Eat at your calculated TDEE for 2 weeks, weighing yourself daily.
- Calculate your average weight each week.
- If you maintained weight: your TDEE estimate is close.
- If you gained: reduce by 150–200 kcal.
- If you lost weight at maintenance: increase by 150–200 kcal.
This takes 2–4 weeks but gives you a personalised number that no formula can match.
Setting Your Deficit or Surplus
Once you have your TDEE:
- Fat loss: eat 300–500 kcal below TDEE for ~0.5–0.8 kg/week loss (sustainable)
- Aggressive cut: 500–750 kcal below TDEE for ~0.75–1.0 kg/week (higher muscle loss risk)
- Muscle gain: eat 200–300 kcal above TDEE (minimises fat gain while building muscle)
- Maintenance: eat at TDEE
A 7,700 kcal deficit = approximately 1 kg of fat. That's the maths.
Why TDEE Changes Over Time
Expect your TDEE to decrease as you lose weight — because you're carrying less mass, your BMR falls proportionally. A person who drops from 90 kg to 80 kg burns roughly 100–150 fewer calories per day at the new weight.
This is why diets that worked at the start stop working later. It's not a plateau from eating the wrong foods — it's a TDEE recalibration problem.
Transpir back-calculates your actual TDEE from your real weight trend. If you're losing slower than projected, the system detects the gap and surfaces it — so you know to adjust before you stall.
The Bottom Line
TDEE is the foundation. Before you cut carbs, add cardio, or try intermittent fasting, know your TDEE. The formula gives you a starting estimate; tracking gives you the real number. Everything else — deficit size, food choices, workout volume — is secondary.
Log your weight daily, eat consistently, and let the trend tell you the truth.