Your Total Daily Energy Expenditure (TDEE) is the number of calories your body burns in a day — through basic metabolism, daily activity, and exercise. Once you know that number, setting a calorie target becomes simple arithmetic: eat below it to lose weight, at it to maintain, or above it to gain. The hard part isn't the math — it's choosing a realistic deficit or surplus and sticking with it.
From TDEE to calorie target
- Weight loss: subtract 300–500 kcal from your TDEE. A 500 kcal/day deficit produces roughly 0.45 kg (1 lb) of weight loss per week. A 300 kcal/day deficit is slower but more sustainable.
- Maintenance: eat at your TDEE. Weight should stay roughly stable over 2–4 weeks (daily fluctuations of 0.5–1.5 kg from water and food are normal).
- Weight gain: add 200–500 kcal above your TDEE. For muscle gain, aim for the lower end (200–300 kcal surplus) to minimize fat gain. For general weight gain, the higher end works.
A worked example
A 30-year-old woman, 65 kg, 165 cm, moderate exercise (3–5 days/week): BMR ≈ 1,400 kcal (Mifflin-St Jeor). TDEE = 1,400 × 1.55 ≈ 2,170 kcal/day. For steady weight loss: 2,170 − 500 = 1,670 kcal/day. That's roughly 4 meals of 400 kcal, or 3 meals of 500 kcal with a 170 kcal snack. For maintenance: stay around 2,170 kcal/day and adjust if weight trends up or down over 2–4 weeks.
Why the number is an estimate, not a prescription
- The BMR formula (Mifflin-St Jeor) is accurate to ±5–10% for most people, but body composition matters — muscular people burn more at rest than the formula predicts, and very sedentary people burn less.
- The activity multiplier is a guess. Most people overestimate their activity. If you chose 'moderate exercise' but your actual workouts are light walks, your TDEE is probably lower.
- Thermic effect of food (TEF) is usually baked into TDEE estimates but varies by diet — protein has a higher TEF (20–30%) than carbs (5–10%) or fat (0–3%).
- Metabolic adaptation — as you lose weight, your BMR drops too, so a static TDEE becomes stale. Recalculate every 5–10 kg of weight change.
Use the scale as feedback, not the calculator
The TDEE formula gets you within 10–15% of your actual calorie needs. The remaining gap is closed by tracking your weight over 2–4 weeks and adjusting your intake by 100–200 kcal in the direction you need. The calculator starts the process; the scale finishes it.
Setting macros within your calorie target
Once you have a calorie number, the next question is what to eat. A common starting point: 25–30% of calories from protein (to preserve muscle during a deficit), 25–35% from fat (for hormones and satiety), and the rest from carbs (for energy). These are starting points — adjust based on how you feel, your training demands, and your preferences.
Don't go below 1,200 kcal (women) or 1,500 kcal (men)
Very low calorie diets risk nutrient deficiencies, muscle loss, metabolic slowdown, and hormonal disruption. If your calculated deficit puts you below these thresholds, use a smaller deficit (200–300 kcal instead of 500) and accept slower weight loss. Health is the priority.
Calculate your TDEE and macros
Health Metrics Studio calculates BMR, TDEE, macros, and healthy weight range in one place — all locally in your browser.
Open Health Metrics StudioWhy a single weigh-in is noise and a weekly average is signal
Day-to-day body weight swings by a kilogram or two from water retention, food still in the digestive system, sodium intake, and (for many women) the menstrual cycle — none of which reflects an actual change in body fat. A single Tuesday-morning reading can go up after a genuinely successful week simply because of water weight, which is exactly why chasing one number leads people to make decisions based on noise rather than a real trend. Weighing at the same time under the same conditions every day and averaging seven days against the previous seven-day average filters out most of that noise and reveals the underlying trend far more reliably than any single reading — this, not the day-to-day number, is what the "track over 2–4 weeks" advice is actually asking you to do.
Diet breaks: planned time back at maintenance
For a deficit that needs to run for many weeks or months, some evidence supports scheduling short planned breaks back at maintenance calories — a week every six to eight weeks, for instance — rather than running one unbroken deficit from start to finish. The rationale is twofold: it gives some relief from the psychological fatigue of sustained restriction, which is a major reason long diets get abandoned, and it may partially offset the metabolic slowdown that accumulates over an extended deficit. This isn't a requirement for shorter cuts, but for anything stretching past a couple of months, planning deliberate breaks in advance tends to work better than treating the whole period as one continuous restriction and hoping willpower holds.