Weight Projection Calculator
Estimate how a sustained calorie deficit or surplus may affect your body weight trajectory over time — using your starting weight, maintenance calories and chosen daily intake.
A weight projection estimates how your body weight is likely to change over a defined time horizon when you consistently consume more or fewer calories than your body expends. Projections use a cumulative energy-balance model: approximately 7,700 kcal of cumulative deficit corresponds to roughly 1 kg of fat mass change. Real-world results are non-linear due to metabolic adaptation, fluid shifts, and individual variation.
How It Works
Your projection begins with your maintenance TDEE — the daily energy burn at your starting weight. This is re-estimated each week as body weight changes, since a lighter body burns fewer calories.
The difference between your daily intake and your TDEE produces either a deficit (weight loss) or surplus (weight gain). A consistent 550 kcal daily deficit translates to approximately 0.5 kg (1 lb) expected loss per week mathematically.
Each weekly period accumulates the net energy balance and converts it to an estimated weight change (7,700 kcal ≈ 1 kg). The TDEE is dynamically recalculated each week to reflect metabolic adaptation as weight changes.
Worked Calculation Examples
The following examples use the Mifflin-St Jeor BMR equation and standard activity multipliers — the same methodology used by the interactive calculators on this site. Figures are estimates for illustrative purposes.
12-Week Projection — Female, 75 kg → goal 68 kg, 500 kcal/day deficit
Starting weight: 75 kg. BMR ≈ 1,489 kcal/day (30F, 168 cm). TDEE (lightly active) ≈ 2,047 kcal/day. Daily intake: 1,547 kcal (−500 deficit).
Projected weight at 12 weeks: approximately 69.5 kg. Estimated time to reach 68 kg goal: ~16 weeks.
As body weight drops, TDEE decreases slightly — meaning the effective deficit narrows over time. Actual results will vary.
8-Week Projection — Male, 90 kg, gaining toward 95 kg, +500 kcal/day surplus
Starting weight: 90 kg. BMR ≈ 1,890 kcal/day (28M, 180 cm). TDEE (moderately active) ≈ 2,930 kcal/day. Daily intake: 3,430 kcal (+500 surplus).
Projected weight at 8 weeks: approximately 93.6 kg. Projected time to reach 95 kg: ~12 weeks.
Gaining weight slows as TDEE rises with increased body mass. Lean mass vs fat ratio depends on training and protein intake.
Get Your Personalized Result
The examples above use reference figures. For results based on your exact age, sex, height, weight and activity level, use the interactive tool.
Simulate My Weight ProjectionContinue Your Nutrition Planning
Weight projections are mathematical estimates based on simplified energy-balance models. Real weight loss is non-linear. Daily fluctuations of 1–3 kg are normal due to water retention, glycogen levels, and sodium intake. Projections do not predict clinical outcomes and do not constitute medical advice.
Common Questions
What is a weight projection?
A weight projection is a mathematical estimate of how your body weight may change over time based on a sustained calorie deficit or surplus relative to your daily energy expenditure (TDEE). It models cumulative energy balance across weeks or months.
How is weight projection calculated?
Each week, the difference between your calorie intake and your TDEE is accumulated. Approximately 7,700 kcal of cumulative deficit equals an estimated 1 kg of fat loss. TDEE is recalculated weekly to account for the fact that a lighter body burns fewer calories.
Why does the scale not match my projected weight loss?
Projections model fat mass change. Day-to-day scale weight is heavily influenced by water retention (especially from carbohydrate intake and sodium), glycogen storage levels, hormonal cycles, and bowel content. Track trends over 2–4 week periods rather than daily readings.
What is metabolic adaptation in weight projection?
As you lose weight, your BMR decreases because a smaller body requires less energy to function. This means your effective calorie deficit shrinks progressively over time — which is why weight loss typically slows as you approach your target. Recalculating your calorie goal periodically helps maintain progress.
How accurate are weight projection calculators?
Weight projection tools provide directionally accurate mathematical estimates under ideal conditions. Real outcomes vary due to genetic metabolic differences, hormonal factors, medication, sleep quality, and adherence consistency. Use projections as planning guides rather than precision predictions.
Medical Disclaimer: All calorie and weight estimates on this page are mathematical projections based on population-level reference equations. They are not medical diagnoses or prescriptions. Individual results vary. Consult a qualified physician or registered dietitian before making significant changes to your diet, especially if you have a medical condition, are pregnant, or are managing a nutritional disorder.