Cutting and bulking both come down to calorie balance (intake − expenditure). Since 1 kg of body fat corresponds to roughly 7,200 kcal, a known daily balance lets you estimate your rate of change. This tool projects your weight over 1–24 weeks from your balance, and can also work backwards from a goal weight and deadline to the daily balance you need.
How to use this tool
First estimate your daily expenditure with the TDEE Calculator, then enter the difference between it and your actual intake (±kcal). Negative to cut (e.g. −300), positive to bulk. If you have a clear goal, use the "work back from goal" mode to see the required balance.
Safe rates of change
For fat loss, 0.5–1.0% of body weight per week is a sustainable pace that preserves muscle (0.35–0.7 kg/week at 70 kg). Faster cuts raise the risk of muscle loss, metabolic slowdown and rebound. For lean bulking, around 0.25–0.5% per week keeps fat gain in check. This tool warns when your pace exceeds 1% per week.
Why reality drifts from the projection
Daily weight swings with water, glycogen and food in transit, and TDEE itself falls as a cut progresses (metabolic adaptation), so real-world change is usually slower than projected. Review your weekly average every 2–4 weeks and adjust the balance. The PFC Calculator helps structure the diet itself.
Why does 1 kg of fat equal about 7,200 kcal?+
That puts 1 kg of body fat at about 7,200–7,700 kcal. This tool uses the widely quoted 7,200 kcal (the same value as the Calories Burned Calculator).
How much can I safely lose per month?+
At 70 kg that is 1.4–2.8 kg per month. Much faster than this raises the risk of muscle loss, hormonal disruption and rebound.
My weight isn’t dropping as calculated. Why?+
1. Water and glycogen swings: daily weight easily moves 1–2 kg with food content
2. Metabolic adaptation: TDEE falls as the cut progresses
3. Underestimated intake: unlogged calories are very common
Judge by weekly averages, and revisit the balance if you stall for 2–4 weeks.
Can I use this for bulking?+
For muscle gain, a slow surplus of about 0.25–0.5% of body weight per week is said to limit fat gain. Check protein needs with the Protein Calculator.
Does the balance have to be the same every day?+
−500 kcal on weekdays and ±0 on weekends averages −357 kcal/day, and the projection applies to that average. Pick a pattern you can sustain.
・Formula: weight change (kg) ≈ cumulative calorie balance (kcal) ÷ 7,200 (1 kg body fat ≈ 7,200 kcal)
・Wishnofsky M. (1958). Caloric equivalents of gained or lost weight. The American Journal of Clinical Nutrition, 6(5), 542–546.
・Helms ER, et al. (2014). Evidence-based recommendations for natural bodybuilding contest preparation. Journal of the International Society of Sports Nutrition, 11, 20.
・Hall KD, et al. (2011). Quantification of the effect of energy imbalance on bodyweight. The Lancet, 378(9793), 826–837.
This simulation uses a simplified model in which only body fat changes at a constant rate. Real weight change is affected by water, muscle mass and metabolic adaptation. Extreme calorie restriction harms health — consult a doctor or registered dietitian before eating below your BMR, or if you have medical conditions or a history of disordered eating.
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