TDEE Explained: What Your Body Actually Burns in a Day

Two numbers, one budget

Your body burns energy all day. **BMR** — basal metabolic rate — is the burn at complete rest: keeping the heart beating, the lungs breathing, the brain running and the body at 37 °C. It typically accounts for 60–70% of daily expenditure. **TDEE** — total daily energy expenditure — adds everything else: walking, typing, training, digesting. TDEE is the number that matters for weight management, because it is your true daily energy budget.

Eat around TDEE and your weight holds steady. Eat below it and you draw on body stores; eat above it and you store the surplus. That is the entire arithmetic of weight change, and no amount of diet branding changes it.

How the estimate is computed

You cannot measure BMR without a lab, so every practical tool estimates it from an equation. The most widely used today is **Mifflin-St Jeor** (1990), which our [Calorie / TDEE Calculator](/calculators/tdee.html) implements:

Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. Women: the same with −161 instead of +5. Validation studies put it within roughly 10% of measured values for most adults — better than the older Harris-Benedict equation, which is why we use it.

TDEE is then BMR × an **activity multiplier**: 1.2 sedentary (desk job, little movement), 1.375 lightly active (light exercise 1–3 days/week), 1.55 moderately active (3–5 days), 1.725 very active (6–7 days or physical job). The multiplier is where most errors enter, because self-assessment drifts upward.

The activity-multiplier trap

A person with a desk job who trains three evenings a week is usually **lightly active (1.375)**, not moderately or very active — three to five hours of exercise per week barely moves a multiplier dominated by 40+ hours of sitting. The honest fix: pick the lower multiplier, watch your weight trend for two weeks, and adjust calories based on the trend, not the estimate.

The same feedback loop handles the other big distortion: eating back exercise calories. Trackers routinely overcount burn by 20–50%. If you must eat some back, eat back half.

Using TDEE for losing or gaining

A deficit of 300–500 kcal below TDEE loses roughly 0.3–0.5 kg per week — the rate at which adherence survives. Cutting 1,000+ kcal below TDEE works briefly and then fails: hunger, muscle loss and metabolic adaptation conspire. For gain, a 200–300 kcal surplus builds muscle with minimal fat gain for most trainees; bigger surpluses just add fat faster.

Two mechanical facts people miss. First, **TDEE falls as you lose weight** — a lighter body burns less, so the deficit that worked at 90 kg stalls at 80 kg. Recalculate every 5 kg. Second, metabolism does adapt slightly to sustained deficits ('adaptive thermogenesis'), another reason the deficit should be moderate and the plan patient.

Where the macro split fits

TDEE sets the calorie budget; macronutrients divide it. Our calculator shows an illustrative 40/30/30 carb/protein/fat split. The evidence-based non-negotiables: protein around 1.6–2.2 g per kg of body weight when training, fat no lower than about 20% of calories for hormonal health, and carbs filling the rest according to activity. The exact split matters far less than the budget and the protein floor.

A worked example

Woman, 35, 165 cm, 70 kg, lightly active. BMR = 10×70 + 6.25×165 − 5×35 − 161 = 1,406. TDEE ≈ 1,406 × 1.375 ≈ 1,933 kcal. Fat-loss target: about 1,450–1,600 kcal/day, protein ≈ 112–154 g. Re-run at 65 kg and the new TDEE is ≈ 1,840 — the plan updates itself. Try your own numbers in the [Calorie / TDEE Calculator](/calculators/tdee.html).

Frequently asked questions

**Is BMR the minimum I should eat?** For extended periods, roughly yes — eating far below BMR is unsustainable. **Why do I burn less than my tracker says?** Trackers overestimate; trust your weight trend. **Do I recalculate after losing weight?** Yes, every ~5 kg. **Does muscle raise TDEE?** Modestly — muscle is metabolically active, which is one reason resistance training helps long-term. **Which tool computes this?** The [TDEE Calculator](/calculators/tdee.html) here, with the Mifflin-St Jeor equation.