Working Backward from Your Goal
Most calorie calculators start from your activity level and apply a fixed ±500 kcal — useful, but it does not answer "how many calories do I need to hit 72 kg by my vacation in 12 weeks?" This calculator works backward: it takes your goal weight and timeframe, then tells you the exact daily target that gets you there.
Daily deficit = (start weight − goal weight) × 7,700 kcal/kg ÷ (weeks × 7)
One kilogram of body fat stores roughly 7,700 kcal (about 3,500 kcal per pound). Your Total Daily Energy Expenditure (TDEE) is estimated with the Mifflin-St Jeor equation and an activity multiplier, exactly as in our calorie calculator, then the required deficit is subtracted (or added, for a gain goal).
Worked Example
A 30-year-old woman, 165 cm, 80 kg, moderately active, wants to reach 72 kg in 12 weeks. TDEE ≈ 2,356 kcal. The 8 kg loss requires 8 × 7,700 = 61,600 kcal total, or 61,600 ÷ 84 days ≈ 733 kcal/day — target intake ≈ 1,623 kcal/day, a 0.67 kg/week pace. That deficit and target both sit within the calculator's safety thresholds; pushing the same 8 kg goal into a much shorter timeframe would trigger the aggressive-deficit warning instead.
Why the Safety Check Matters
Deficits beyond roughly 1,000 kcal/day, or targets under about 1,200 kcal (women) / 1,500 kcal (men), risk muscle loss, nutrient deficiency and metabolic slowdown — and are hard to sustain regardless. A milder, longer deficit (300–500 kcal/day) preserves more muscle and is far more likely to stick.
Recalculate as You Go
As you lose weight your TDEE drops too, so a fixed calorie target becomes a smaller and smaller deficit over time. Re-run the numbers every 3–5 kg to keep the pace on track.
Estimates for healthy adults. Consult a professional for medical weight management or before targeting a rapid loss.