Body Weight Planner
Enter your current weight, goal weight, and how many weeks you have. Get a daily calorie target, your expected weekly pace, and a week-by-week milestone schedule.
Enter your stats and goal to build a weight plan.
- Enter your stats. Sex, age, height, current weight, and activity level — these set your TDEE (maintenance calories).
- Enter your goal weight. The weight you want to reach. Lower than current = weight loss plan; higher = weight gain plan.
- Choose a timeline. How many weeks you want to reach your goal. The planner caps the daily deficit at 1,000 kcal and surplus at 500 kcal for safety.
- Read your daily calorie target. You get a daily intake, the required deficit or surplus, your expected weekly pace, and a week-by-week milestone table.
The plan is built from two steps. First, your TDEE (Total Daily Energy Expenditure) is estimated using the Mifflin-St Jeor equation and your activity level — this is how many calories your body uses on a typical day. Second, the planner calculates how much you need to eat above or below that number each day to reach your goal weight in your chosen timeline.
The underlying model treats one kilogram of body fat as storing approximately 7,700 kcal. A daily deficit of 550 kcal, for example, produces a weekly deficit of 3,850 kcal — about half a kilogram of fat loss per week. This is the same energy-balance model used in clinical nutrition research.
The most common mistake in weight loss is setting a deficit that is too aggressive to maintain. Very large deficits — beyond about 1,000 kcal/day — tend to produce faster initial results but cause muscle loss, fatigue, increased hunger, and eventual rebound. The research consistently shows that slower, steadier deficits preserve more lean mass and produce better long-term outcomes.
A practical target for most people is 0.5–1 kg of loss per week, which requires a daily deficit of roughly 500–700 kcal. This is achievable through diet alone or a combination of diet and exercise, without the hunger and fatigue that come with steeper cuts.
Daily weight fluctuates by 1–2 kg or more even with perfect adherence to a plan. The main driver is water: sodium, carbohydrate intake, hydration, and hormonal cycles all shift the amount of water your body retains day to day. This noise sits on top of the underlying fat-loss trend and can completely mask a week of good progress.
The most reliable approach is to weigh yourself at the same time each day — ideally in the morning, after using the bathroom, before eating — and track a rolling 7-day average rather than individual readings. The trend over weeks is what matters, not any single number.
Energy balance model
daily adjustment (kcal) = (goal change kg x 7700) / (weeks x 7)
target calories = TDEE + daily adjustment- 7700
- = kcal stored per kilogram of body fat (approx. 3500 kcal/lb)
- TDEE
- = Total Daily Energy Expenditure (Mifflin-St Jeor BMR x activity factor)
- daily adjustment
- = negative for a deficit (weight loss), positive for a surplus (weight gain)
Safe caps applied: deficit limited to 1,000 kcal/day, surplus to 500 kcal/day. Exceeding these limits increases muscle loss risk (deficit) or excess fat gain (surplus).
How does this calculator work?
It calculates your Total Daily Energy Expenditure (TDEE) using the Mifflin-St Jeor formula, then works out how many calories you need to add or subtract each day to reach your goal weight in your chosen timeline. The math is based on the energy stored in body fat — approximately 7,700 kcal per kilogram — which is the most widely used model in clinical nutrition.
How long does it realistically take to lose weight?
A sustainable rate for most people is 0.5–1 kg (1–2 lbs) per week. That requires a daily deficit of roughly 500–700 kcal, which is achievable through diet alone or a combination of diet and exercise. Faster rates are possible but increase the risk of muscle loss and are harder to sustain. The planner caps the deficit at 1,000 kcal/day as a safety limit and will flag when your goal requires more time at a safe pace.
What is the 7,700 kcal per kilogram rule?
One kilogram of body fat stores approximately 7,700 kilocalories of energy (about 3,500 kcal per pound). Creating a cumulative deficit of 7,700 kcal should therefore result in roughly 1 kg of fat loss. This is an estimate — actual weight change also involves water shifts, changes in lean mass, and metabolic adaptation — but it is the best simple model available without metabolic testing.
Why is there a cap on the daily deficit or surplus?
Very large deficits — typically beyond 1,000 kcal/day — increase the proportion of weight lost from lean muscle rather than fat, and are associated with nutrient deficiencies, fatigue, and eventual rebound weight gain. For surpluses, going beyond about 500 kcal/day over maintenance tends to produce more fat gain relative to muscle. The caps are guideline values, not absolute medical limits, but they reflect standard practice in clinical nutrition.
Will I actually lose exactly this much per week?
Probably not exactly, and that is normal. Weight fluctuates day to day due to water retention, sodium intake, hormonal cycles, and digestion. The weekly milestones are the expected average trend — if you weigh yourself daily, expect noise around that trend rather than a smooth line. Weighing weekly, at the same time and conditions, gives a better picture of actual progress.
How is this different from the Calorie Deficit Calculator?
The Calorie Deficit Calculator lets you choose a deficit size and tells you how much you would lose. This planner works the other way: you enter a goal weight and a deadline, and it tells you what deficit is needed. Use this one when you have a specific target and timeline; use the Calorie Deficit Calculator when you want to explore different deficit sizes and their effects.
Can I use this to plan weight gain?
Yes. Enter a goal weight higher than your current weight and the planner switches to a surplus. A daily surplus of 250–500 kcal above maintenance is a common recommendation for lean bulking — enough to support muscle growth while minimizing excess fat gain. The planner caps the surplus at 500 kcal/day for this reason.
Do I need to adjust my target as I lose weight?
Yes, periodically. As your weight drops, your TDEE decreases — a lighter body burns fewer calories at rest and during movement. This is why weight loss tends to slow over time even with a consistent intake. Recalculating every 5 kg (10 lbs) of weight change is a reasonable rule of thumb to keep your target current.
References
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247.
- Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826-837.
FitCalcs calculators provide general estimates for healthy adults and are not medical advice.
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