Weight loss timeline
See roughly how long it will take to reach your goal weight, and what to expect along the way.
How the estimate works
Losing a kilogram of body weight takes a cumulative deficit of roughly 7,700 kcal (about 3,500 kcal per pound). The calculator divides the weight you want to lose by your weekly deficit to get the number of weeks.
That rule is a useful first approximation but it overestimates long-term loss, because your energy needs fall as you get lighter. Research by Kevin Hall and colleagues at the NIH quantified this; for a dynamic prediction, try the NIH Body Weight Planner.
In practice, the most reliable way to stay on schedule is to check your weekly trend and adjust your intake when it stalls. PromptlyFit's coach does that check with you inside your AI assistant.
Frequently asked questions
How long will it take to reach my goal weight?
It depends on your daily calorie deficit. A 500 kcal daily deficit gives roughly 0.45 kg (1 lb) a week at first. This tool shows the straight-line estimate; real loss usually slows over time.
Why does weight loss slow down?
As you lose weight, you burn fewer calories, so the same intake produces a smaller deficit. Researchers at the NIH built models showing this; their Body Weight Planner accounts for it.
What is a safe rate of weight loss?
For most people, about 0.5 to 1 kg (1 to 2 lb) a week. Faster loss makes it harder to keep muscle and stick with the plan.
Why does the scale jump around day to day?
Water, salt, carbohydrate and digestion can move your weight by a kilogram or more from one day to the next. Look at the weekly trend, not single weigh-ins.
Sources
- Hall KD, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011.
- NIH NIDDK Body Weight Planner
These calculators give estimates for healthy adults and aren't medical advice. If you're pregnant, under 18, or managing a medical condition, talk to a doctor or registered dietitian before changing how you eat.