What Is TDEE and How Is It Calculated?

TDEE — Total Daily Energy Expenditure — is the number most calorie targets are built on, but it's often confused with BMR or treated as a single fixed number when it's really an estimate that shifts with your routine.

TDEE vs BMR: what's the difference

BMR (Basal Metabolic Rate) is the energy your body burns at complete rest just to keep organs running, breathing, and circulating blood — no movement included. TDEE takes that baseline and adds everything else: walking, exercise, fidgeting, digestion, and daily activity. TDEE is always higher than BMR, and it's the number that actually matters for setting a calorie target, since almost nobody is lying perfectly still all day.

How BMR is calculated

The most widely used formula today is Mifflin-St Jeor, which replaced the older Harris-Benedict equation for most clinical and fitness use because it tends to estimate closer to measured values:

For a 30-year-old woman who is 165cm and 65kg: BMR = 10×65 + 6.25×165 − 5×30 − 161 ≈ 1,401 calories per day at complete rest.

Turning BMR into TDEE with an activity multiplier

TDEE is calculated by multiplying BMR by an activity factor that reflects how much you move in a typical week:

• 1.2 — Sedentary (little to no exercise, desk job)
• 1.375 — Lightly active (light exercise 1–3 days/week)
• 1.55 — Moderately active (moderate exercise 3–5 days/week)
• 1.725 — Very active (hard exercise 6–7 days/week)
• 1.9 — Extremely active (physical job plus daily training)

Using the same example, a lightly active person's TDEE would be roughly 1,401 × 1.375 ≈ 1,926 calories per day — the estimated number of calories needed to maintain her current weight.

Using TDEE to lose, maintain, or gain weight

Once you have TDEE, it becomes the baseline for a calorie target: eating at TDEE roughly maintains weight, eating below it creates the deficit needed for weight loss, and eating above it supports weight gain. A common, moderate approach is a 500 calorie/day deficit for gradual weight loss (roughly 0.45kg per week) rather than a large, hard-to-sustain cut.

Why TDEE is an estimate, not a measurement

Every formula-based TDEE number is a population-level estimate — real-world energy expenditure varies with genetics, muscle mass, sleep, stress, and non-exercise movement that's hard to quantify. Treat the number as a starting point: track actual weight change over 2–3 weeks at a given calorie level and adjust from there rather than assuming the formula is exact on day one.