BMR vs TDEE — the two numbers people confuse
Your BMR (Basal Metabolic Rate) is the energy your body would burn lying perfectly still all day — the cost of being alive. Your TDEE (Total Daily Energy Expenditure) is what you actually burn: BMR plus digesting food, walking around, and exercise. Calorie targets for losing, maintaining or gaining weight should always be built from TDEE. This calculator estimates BMR with the Mifflin-St Jeor equation, then scales it:
BMR = 10 × kg + 6.25 × cm − 5 × age + 5 (men) or − 161 (women)
TDEE = BMR × activity multiplier (1.2 – 1.9)
Worked example
A 30-year-old man, 70 kg (154 lb), 170 cm (5′7″) has a BMR of about 1,618 kcal. Moderately active (3–5 workouts a week), his TDEE is 1,618 × 1.55 ≈ 2,507 kcal/day. Sedentary, the same man burns only about 1,941 kcal — a 566-kcal difference that explains why the multiplier matters more than any other input.
How to pick your level honestly
Almost everyone overestimates. A desk job plus a daily dog walk is sedentary, not lightly active. Count only structured training and genuinely physical work: three gym sessions a week with an office job is lightly-to-moderately active; "very active" means hard training nearly every day; "extra active" is reserved for labourers who also train, or two-a-day athletes. When torn between two levels, choose the lower one and let two weeks of scale data settle the argument.
Limitations
The estimate is typically within ±10% but can miss by more for very muscular, very lean or very sedentary people, and the multipliers are coarse brackets. Treat the output as a hypothesis: track intake and body weight for two to three weeks — a stable weight means you found your real TDEE, whatever the formula said.