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.
Built and reviewed by Jesse · Last reviewed
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 applies general daily-adjustment guardrails of a 1,000 kcal deficit and a 500 kcal surplus.
- 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 — may produce faster initial results but can increase muscle loss, fatigue, and hunger. A slower adjustment is often easier to sustain.
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. For a realistic sense of what that trend looks like over months, see the guide on how long it takes to lose weight.
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)
Planning guardrails applied: deficit limited to 1,000 kcal/day and surplus to 500 kcal/day. These are general limits, not individualized medical safety thresholds.
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 gradual rate is easier for many people to sustain. Faster rates can increase the risk of muscle loss and may be harder to maintain. The planner uses a general 1,000 kcal/day deficit guardrail and flags when the requested timeline would require a larger adjustment; this is not an individualized medical safety limit.
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 can increase fatigue and the risk of losing lean mass, while large surpluses may add more fat relative to muscle. The planner therefore uses general adjustment guardrails of a 1,000 kcal/day deficit and a 500 kcal/day surplus. They are planning defaults, not individualized medical limits.
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.
What if I do not know what goal weight to pick?
This planner assumes you already have a target in mind — it works out the calories and timeline to reach it. If you are still deciding what that target should be, start with the Ideal Weight Calculator, which shows a healthy weight range for your height and sex, then bring a number from that range back here to build the plan. Picking a goal from a healthy range rather than a single figure tends to produce a more realistic timeline.
How is this different from the NIDDK Body Weight Planner?
The NIDDK (National Institute of Diabetes and Digestive and Kidney Diseases) Body Weight Planner uses a more complex mathematical model that accounts for metabolic adaptation — the way your metabolism slows as you lose weight. This planner uses the simpler energy-balance model (7,700 kcal per kilogram of fat), which is accurate enough for planning a realistic target and timeline. For most people the two tools give similar results over a 12-week horizon. The NIDDK model is more precise for longer timelines where metabolic adaptation becomes a meaningful factor.
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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