Overview
Losing fat means eating fewer calories than you burn. This calculator turns your goal weight and chosen pace into the daily deficit you need and how long it will take, based on roughly 7,700 kcal per kilogram of body mass.
How it's calculated
Enter your current weight, goal weight and a weekly rate of change (0.5 kg/week is a sustainable default). We compute the daily calorie deficit and project the number of weeks and months to reach your goal. It also works for gaining weight.
daily deficit = weekly rate × 7700 / 7 weeks = |current − goal| / weekly rate
How to read your result
A 0.25–0.75 kg/week loss is sustainable for most people; faster than ~1% of bodyweight per week risks muscle loss. The timeline is an estimate — real progress is rarely perfectly linear, so reassess every few weeks.
Frequently asked questions
How big should my deficit be?
A deficit producing 0.25–0.75 kg of loss per week suits most people. Aggressive deficits work short-term but are harder to sustain and risk muscle loss.
Why 7,700 kcal per kg?
It's the common approximation for the energy in a kilogram of body mass. It's not exact for everyone, but it's a reliable planning figure.
Can I use this to gain weight?
Yes — set a goal heavier than your current weight and the result becomes a daily surplus with the same timeline math.
Sources & references
- Hall KD, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826-837.
- Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr. 1958;6(5):542-546.
Medical disclaimer
This calculator is for general educational purposes only and is not medical advice. Estimates are based on population formulas and may not fit your individual situation. Consult a qualified healthcare or fitness professional before making health, nutrition or training decisions.