If you've ever wondered how many calories you should eat in a day, the answer starts with TDEE — your Total Daily Energy Expenditure. It's the total number of calories your body uses in 24 hours, and once you know it, setting a goal becomes simple arithmetic. Let's break it down.
Step 1: Your BMR
BMR (Basal Metabolic Rate) is what you'd burn at complete rest — just keeping your heart, lungs, and brain running. The most reliable everyday estimate is the Mifflin-St Jeor equation:
- Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
- Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
For a 30-year-old woman who is 165 cm and 65 kg:
- 10 × 65 = 650
- 6.25 × 165 = 1,031
- 5 × 30 = 150
- 650 + 1,031 − 150 − 161 = 1,370 calories/day
Step 2: Multiply by your activity factor
BMR only covers rest. To get TDEE, multiply by a factor that reflects how active you are:
- Sedentary (little/no exercise): × 1.2
- Lightly active (1–3 days/week): × 1.375
- Moderately active (3–5 days/week): × 1.55
- Very active (6–7 days/week): × 1.725
- Extra active (hard daily training or physical job): × 1.9
Our example woman, lightly active, has a TDEE of 1,370 × 1.375 ≈ 1,884 calories/day. That's roughly what she needs to maintain her current weight.
Step 3: Adjust for your goal
TDEE is your maintenance line. From there:
- Lose weight: eat below TDEE, often a 300–500 calorie deficit per day (about 0.25–0.5 kg per week).
- Maintain: eat around your TDEE.
- Gain weight/muscle: add roughly 250–500 calories per day.
A pound of fat holds about 3,500 calories, so a 500-calorie daily deficit trends toward about 0.5 kg (1 lb) lost per week. Steady, modest changes are easier to sustain than crash diets.
How to use it
Skip the hand math with the Calorie (TDEE) Calculator. Enter your age, height, weight, sex, and activity level, and it returns your maintenance calories along with weight-loss and weight-gain targets.
To round out the picture, the BMI Calculator tells you whether your current weight sits in a healthy range, which helps you decide which TDEE target makes sense. And since activity raises both calorie and fluid needs, the Water Intake Calculator is a handy companion for staying hydrated as you train.
A few honest caveats
TDEE formulas are population averages. Your real burn can vary by 10% or more depending on genetics, body composition, and how accurately you judge your activity level. Treat the number as a starting estimate, weigh yourself over a couple of weeks, and adjust based on what actually happens.
These figures are general estimates, not medical or dietary advice. If you have a medical condition or want a tailored nutrition plan, check in with a doctor or registered dietitian.