How many calories should you eat? This TDEE calculator answers that with the Mifflin–St Jeor equation — the predictive formula the American Dietetic Association found most accurate for resting metabolism — then multiplies by your activity level to get your Total Daily Energy Expenditure and calorie targets for losing, maintaining or gaining weight.
BMR vs TDEE — what's the difference?
Your BMR (Basal Metabolic Rate) is the energy your body burns at complete rest just keeping you alive — breathing, circulation, cell repair. Your TDEE adds everything else: walking, working, training, even digesting food. Eating roughly at your TDEE maintains your weight; below it you lose, above it you gain.
How the calculation works
In the equation, s = +5 for men and −161 for women. Worked example: a 30-year-old woman, 165 cm and 65 kg, has BMR = 10×65 + 6.25×165 − 5×30 − 161 = 1,370 kcal. With moderate exercise (×1.55), her TDEE is about 2,124 kcal/day — her maintenance calories.
Choosing your activity level honestly
The multipliers run from 1.2 (sedentary desk job, little exercise) through 1.375 (light exercise 1–3 days/week), 1.55 (moderate, 3–5 days), 1.725 (hard, 6–7 days) to ~1.9 (very hard training or physical job). Most people overestimate — when in doubt, pick the lower level and adjust based on real-world results after a few weeks.
Calories to lose, maintain or gain
A deficit of about 500 kcal/day below TDEE typically produces ~0.45 kg (1 lb) of loss per week; a similar surplus supports gradual muscle gain. Larger deficits are harder to sustain and can cost muscle. Recalculate as your weight changes — TDEE falls as you get lighter. Pair this with the BMI calculator and ideal weight calculator to set sensible targets.
Estimates for general information only — not medical or nutritional advice.
Where the activity multipliers come from
The multipliers (1.2 sedentary through ~1.9 very active) scale your BMR into a full day's burn, and they descend from published physical-activity-level (PAL) research rather than gym folklore. The classic mistake is grading yourself on workouts alone: three gym sessions a week atop a desk job is "lightly active" (~1.375), not "very active" — the multiplier prices your whole week, sleep and commute included. If you're between levels, pick the lower one and observe: your weight trend over 3–4 weeks is the real calorimeter, and a 200–300 kcal adjustment is one level's worth of correction.