Weight-Loss Timeline Calculator (Calorie Deficit)
Enter your current weight, target weight and daily calorie deficit. The tool projects how many weeks the goal will take, the expected goal date, and the weekly loss rate with a sustainability rating.
Enter a valid current weight (> 0), target weight (> 0 and below current) and daily deficit (> 0).
Weeks to goal
20.0
140 days
Expected goal date
—
Starting from today.
Avg weekly loss
0.5 kg
0.6% / week
Pace assessment
—
Rules of thumb
- 1 kg of body fat ≈ 7 700 kcal; 1 lb ≈ 3 500 kcal (Wishnofsky rule of thumb).
- A 500 kcal/day deficit averages roughly 0.45 kg / 1 lb of loss per week.
- CDC and NHS recommend 0.5–1 kg (1–2 lb) per week as the most maintainable pace.
Estimates only. Real-world loss diverges from the linear model due to metabolic adaptation, water shifts and changes in lean mass — consult a doctor or dietitian for a personalised plan.
Formula
days = (current weight − target weight) × kcal per unit ÷ daily deficit
- · Uses the Wishnofsky rule of thumb: 1 lb of body fat ≈ 3 500 kcal, 1 kg ≈ 7 700 kcal.
- · CDC and NHS recommend losing 0.5–1 kg (1–2 lb) per week, roughly a 500 kcal/day deficit.
- · Pace rating uses weekly loss as a % of bodyweight: < 0.5 % gentle, 0.5–1 % recommended, 1–2 % aggressive, > 2 % too fast.
- · The linear estimate ignores metabolic adaptation, water shifts and lean-mass changes — real curves usually flatten.
- · Extreme deficits (> 1 000 kcal/day) are hard to sustain and can hurt hormones, sleep and mood.
- · Use as a planning sanity check; consult a registered dietitian or doctor for personalised advice.
Frequently asked
Is the "3,500 kcal = 1 pound of fat" rule actually accurate?
It was proposed by Max Wishnofsky in 1958 as a rough estimate. Clinical research (Hall 2008, Thomas et al 2014) shows the body adapts and actual loss is slower over time, but the rule is still a useful starting estimate for planning.
Why does weight loss start fast and then slow down?
The first 1–2 weeks are mostly water and glycogen (water bound to stored carbs). After that, your body lowers its basal metabolic rate (adaptive thermogenesis), shrinking the real daily deficit over time.
What size of daily deficit should I aim for?
Common guideline: do not eat below ~1,200 kcal/day for women or ~1,500 kcal/day for men. A 250–500 kcal deficit is usually the most maintainable, 500–1,000 kcal is aggressive, and > 1,000 kcal is hard to sustain without nutrient gaps.
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