Formula
Days = (current weight − goal weight) × 7,700 kcal/kg ÷ daily deficitWeekly loss = daily deficit × 7 ÷ 7,700 kcal/kg How it works
This calculator uses the classic energy-balance rule of thumb: a kilogram of body fat holds about 7,700 kcal (roughly 3,500 kcal per pound). Divide the energy stored in the weight you want to lose by your daily calorie deficit and you get the number of days it should take.
In practice the rule overestimates long-term progress. As you lose weight your maintenance calories drop, so a fixed intake produces a shrinking deficit, and the body adapts in other ways too. Early weeks often show faster loss because of water and glycogen, followed by slower, steadier change. Treat the date as an optimistic target and recalculate as you go.
Most guidelines suggest losing about 0.5–1% of your body weight per week, which for many people means a deficit of 300–750 kcal a day. Larger deficits make it harder to keep muscle and get enough nutrients. This tool is for general information and is not medical advice.
Frequently asked questions
How do I know my daily deficit?
Estimate your maintenance calories with the TDEE calculator, then subtract what you actually eat. For example, a TDEE of 2,500 kcal and an intake of 2,000 kcal is a 500 kcal deficit.
Can exercise count toward the deficit?
Yes — the deficit is the gap between calories burned and eaten. Just be careful not to overestimate exercise calories, which fitness trackers often do.