About this calculator
This calculator targets a daily calorie intake for a specific weight-change goal. It computes your TDEE (total daily energy burn) and adjusts by 500 calories per pound per week of intended change. 1 lb of body fat ≈ 3,500 calories, so a 500-cal/day deficit averages 1 lb/week loss in steady state.
Realistic weekly rates
- 0.5–1 lb/week loss — Sustainable, preserves muscle, low rebound risk. Default for most.
- 1–2 lb/week loss — Aggressive but doable for higher body-fat individuals or short timeframes. Higher muscle-loss risk; protein priority matters more.
- 2+ lb/week loss — Only sustainable for very high body fat starting points, or short medical-supervision contexts. Most "rapid" diets at this rate fail within 6 months.
- 0.5 lb/week gain — Lean bulk for muscle building. Most of the gain should be muscle if training stimulus and protein are adequate.
- 1+ lb/week gain — Aggressive bulk. Much of the gain will be fat above ~0.5–1% of bodyweight/month.
The 3500-calorie rule, with caveats
The "1 lb = 3500 cal" rule comes from the energy content of body fat, but it ignores metabolic adaptation. Sustained deficits cause TDEE to drop 10–20% over 12+ weeks — so the same deficit produces less weight loss as the diet progresses. Expect to need to either eat less or move more after extended dieting.
Why the 1200-cal floor exists
Below ~1200 cal/day for women / 1500 cal/day for men, it’s hard to hit micronutrient needs and adherence often collapses. Very-low-calorie diets work in clinical contexts (under medical supervision with protein supplementation), but for general self-directed dieting, this calculator clamps at 1200 to avoid recommending an unsustainable plan.
Beyond calories
Two people eating the same calories can have wildly different outcomes based on food quality, meal timing, sleep, stress, and exercise. Calories are the dominant lever — but assuming the lever works in isolation produces mediocre results. Track weight trends weekly, adjust monthly.