Your daily calorie target, macros, and weight-change timeline, powered by three science-backed formulas. No jargon, just the numbers you need.
Two people eating 2,000 calories per day can have dramatically different body composition results depending on what those calories are made of. Protein-rich diets preserve muscle during weight loss, improve satiety, and have a higher thermic effect, your body burns roughly 25-30% of protein calories just digesting them vs 6-8% for carbs and 2-3% for fat. Prioritize protein at every meal and the calorie deficit becomes much easier to sustain.
Your resting calorie burn (technically called BMR, Basal Metabolic Rate) is the number of calories your body burns just to stay alive: heartbeat, breathing, organ function. Think of it as your body's idle engine running 24/7. Three validated formulas estimate this: heartbeat, respiration, organ function, and thermoregulation. Three validated equations are used to estimate it, each with different data requirements and accuracy profiles.
| Formula | Published | Best For | Accuracy |
|---|---|---|---|
| Mifflin-St Jeor | 1990 | General population; most people | ±10% vs indirect calorimetry |
| Harris-Benedict | 1919 / rev. 1984 | Historical standard; still widely used | ±10–15% |
| Katch-McArdle | 1975 | Athletes; when body fat % is known | ±5% if BF% is accurate |
The Mifflin-St Jeor equation (1990) is currently recommended by the Academy of Nutrition and Dietetics as the most accurate for most people. It was derived from a sample of 498 adults and revised for modern populations. Male: BMR = 10×kg + 6.25×cm − 5×age + 5. Female: BMR = 10×kg + 6.25×cm − 5×age − 161.
The Harris-Benedict equation was originally published in 1919 and revised by Roza and Shizgal in 1984. It tends to overestimate BMR by 5% for most people, but remains the most cited equation in clinical nutrition literature.
The Katch-McArdle formula bypasses the limitations of weight-and-height-based equations by using lean body mass directly: BMR = 370 + 21.6 × LBM(kg). This makes it the most accurate option for athletes and muscular individuals who would otherwise be overestimated by BMI-dependent equations.
Your total daily calorie burn (called TDEE) is your resting burn multiplied by how active you are. This accounts for all movement throughout the day, not just formal exercise but non-exercise activity thermogenesis (NEAT): fidgeting, walking, standing, and occupational movement. Most people underestimate their activity level. When in doubt, select one level lower than you think and adjust based on real-world results.
| Level | Multiplier | Description |
|---|---|---|
| Sedentary | 1.2× | Desk job, minimal movement, no formal exercise |
| Lightly active | 1.375× | Light exercise 1–3 days/week or active job with light duties |
| Moderately active | 1.55× | Moderate exercise 3–5 days/week (most gym-goers) |
| Very active | 1.725× | Hard training 6–7 days/week or physically demanding job |
| Extra active | 1.9× | Twice-daily training, elite athlete, or extremely physical work |
Once you have your TDEE, adjusting calories is straightforward. Since one pound of fat stores approximately 3,500 calories (one kilogram approximately 7,700 calories), so eating 500 fewer calories per day produces roughly 0.45 kg / 1 lb of fat loss per week. The calculator applies these deficits and surpluses:
| Goal | Adjustment | Expected Change | Notes |
|---|---|---|---|
| Aggressive Loss | −750 calories/day | ~0.7 kg / 1.5 lbs/week | Requires higher protein; muscle loss risk increases |
| Moderate Loss | −500 calories/day | ~0.45 kg / 1 lb/week | Optimal for preserving lean mass |
| Maintenance | 0 | No change | Eat at TDEE; ideal for recomp with resistance training |
| Lean Gain | +250 calories/day | ~0.25 kg / 0.5 lbs/week | Minimizes fat gain; slower muscle accrual |
| Muscle Gain | +500 calories/day | ~0.45 kg / 1 lb/week | Faster gains; expect ~50% lean / 50% fat in surplus |
Protein is the most important macro to get right. The general recommendation for active individuals is 1.6–2.2 g per kg of body weight per day (0.72–1.0 g/lb). In a caloric deficit, higher protein intake (up to 2.4 g/kg) helps preserve lean muscle. Protein provides 4 calories per gram.
Carbohydrates are the body’s preferred fuel for high-intensity exercise. After meeting protein needs, the remainder of non-fat calories should largely come from carbohydrates for most active people. Carbs provide 4 calories per gram.
Fat is essential for hormone production, fat-soluble vitamin absorption (A, D, E, K), and cell membrane integrity. A minimum of 20–25% of total calories from fat is recommended to maintain hormonal health. Fat provides 9 calories per gram.
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