Explore a weight-loss planning scenario by weekly pace or goal date. Compare calorie estimates as body weight changes, review milestones, and see when a goal falls outside this tool's general-use limits.
- Pace or goal-date mode
- Published dynamic framework
- Milestone schedule
- General-use safety checks
Goal Weight and Timeline Planner
The tool implements the published Hall adult weight-change equations to estimate a constant intake, a changing weight path and long-run maintenance after the goal. It is an independent educational implementation, not the official NIDDK Body Weight Planner.
Estimated goal date October 29, 2026 at 0.45 kg per week
Progress milestones
Goal: 84 kgMilestone timing follows the model's curved weight path. Real intake, activity, health and short-term scale variation can differ, so the dates remain estimates.
Milestone schedule
| Milestone | Modelled date | Modelled weight | Modelled BMI |
|---|---|---|---|
| Start | July 27, 2026 | 90 kg | 29.4 |
| 25% complete | August 8, 2026 | 88.5 kg | 28.9 |
| 50% complete | September 2, 2026 | 87 kg | 28.4 |
| 75% complete | September 30, 2026 | 85.5 kg | 27.9 |
| Goal | October 29, 2026 | 84 kg | 27.4 |
Model and calorie summary
| Measure | Estimate | How to interpret it | Status |
|---|---|---|---|
| Plan intake | 2,325 kcal/day | Constant model input during the planning window | Shown |
| Intake change | −596 kcal/day | Difference from estimated current maintenance | 20.4% |
| Goal maintenance | 2,781 kcal/day | Modelled long-run intake that maintains 84 kg | Separate from plan intake |
| Goal check | 84 kg after 93.3 days | Result of re-running the solved model input | Within 0.01 kg |
Input and result details
| Item | Value | Role |
|---|---|---|
| Model | Published Hall adult model | Models tissue, glycogen, fluid and adaptive responses |
| Baseline inputs | Male coefficients, age 35, height 175 cm | Mifflin resting energy and body-fat regression |
| Current to goal | 90 kg to 84 kg | 6 kg or 6.7% planned change |
| Current and goal BMI | 29.4 to 27.4 | General-use underweight checks |
| Activity assumption | Light PAL, 1.60 | Scales resting energy and the model's activity term |
| Planning pace | 0.5% or 0.45 kg/week | Creates the timeline and energy-gap estimate |
Calculation steps
- Use age 35 years, height 175 cm, current weight 90 kg and goal weight 84 kg.
- Convert 0.5% of starting weight to 0.45 kg/week. Six kilograms at that average pace takes about 13.33 weeks.
- Estimate resting energy with exact Mifflin coefficients: 9.99 x 90 + 6.25 x 175 - 4.92 x 35 + 5 = 1,825.65 kcal/day.
- Estimate current maintenance: 1,825.65 x 1.60 = 2,921.04 kcal/day.
- Estimate initial body fat as 27.09%, or 24.38 kg, with the model's published regression.
- Integrate the fat, lean, glycogen, fluid and adaptation equations in 0.5-day steps. Binary search finds the constant intake that reaches 84 kg after 93.33 days.
- Estimate plan intake at 2,325.38 kcal/day, a reduction of 595.66 kcal/day from baseline. A separate long-run solve estimates goal maintenance at 2,780.76 kcal/day.
- Display 13.3 weeks and October 29, 2026 as a modelled scenario, not a promised outcome.
Recent calculations
Results stay in this page session. Nothing is sent or stored by this calculator.
How to Use This Weight Loss Planner
- Select the published male or female coefficient set used by the Mifflin baseline and body-fat regression.
- Enter adult age, height, current weight and a lower goal weight. Choose metric or US units.
- Select an activity multiplier based on your usual work, transport, household movement and exercise across a normal week.
- Plan from a weekly percentage pace or choose a future goal date. Date mode calculates the pace required by that date.
- Select Build Weight-Loss Plan. Review the timeline, calorie range, milestone table, equation comparison and safety messages.
- Use the result as a starting scenario. Review actual trends and health needs with a qualified professional when appropriate.
Use recent measurements. Do not select a high activity factor from one hard workout. If the activity factor already includes exercise, do not add the same exercise calories again. A longer target does not remove the uncertainty in energy equations, activity estimates or food tracking.
What This Weight Loss Planner Estimates
The planner connects four estimates: resting energy, whole-day maintenance energy, a selected planning window and a modelled weight path. It estimates current resting energy with Mifflin-St Jeor, applies a physical activity level, then numerically solves the published Hall adult equations for a constant calorie intake that reaches the entered goal at the end of the selected window.
The model tracks fat, lean tissue, glycogen, glycogen-associated water, extracellular fluid and adaptive thermogenesis. It produces a separate long-run goal-maintenance estimate because intake during weight loss is not the same as intake estimated to maintain the lower weight. Age, height, coefficient set, PAL, carbohydrate share and sodium assumption stay constant in this public scenario.
Weight Loss Planner Formula
Energy gap = intake − expenditure − glycogen energy flux
Fat and lean change = partitioned energy gap ÷ tissue energy density
Required plan intake = numerical solution that reaches goal weight at time t
The Hall appendix defines the coupled differential equations and constants. This calculator uses a 0.5-day Euler step, re-runs the model during a binary search for intake, and checks that the final modelled weight is within 0.01 kg of the goal. A second 4,000-day solve estimates long-run goal maintenance.
Resting-energy equations
The model uses Mifflin-St Jeor to establish baseline resting energy. The calculator keeps the coefficients used in the cited model description, with weight W in kilograms, height H in centimetres and age A in years:
Female: RMR = 9.99W + 6.25H − 4.92A − 161
Estimated current maintenance equals RMR multiplied by PAL. Neither value measures your metabolism or free-living expenditure. Error in baseline maintenance directly affects the displayed intake, so use the number as a starting estimate.
Worked weight loss planning example
Consider a 35-year-old using the male coefficient set, height 175 cm, current weight 90 kg, goal weight 84 kg and PAL 1.60. A selected pace of 0.5% of starting weight is 0.45 kg/week. The six-kilogram change creates a 93.33-day planning window:
Current maintenance = 1,825.65 × 1.60 = 2,921.04 kcal/day
Modelled constant intake = 2,325.38 kcal/day
Initial maintenance difference = 2,921.04 − 2,325.38 = 595.66 kcal/day
The model estimates long-run goal maintenance near 2,780.76 kcal/day, separate from plan intake. It reaches 88.5 kg near day 11.62, 87 kg near day 36.68 and 85.5 kg near day 64.06 before reaching 84 kg at day 93.33. The early path includes modelled glycogen and fluid responses, but the displayed intake and dates remain estimates.
Weekly Pace vs Goal Date
| Planning method | You choose | The planner estimates | Main limitation |
|---|---|---|---|
| Weekly pace | A percentage of starting weight per week. | Approximate weeks, goal date, modelled intake and milestones. | The selected pace is averaged across the full window. |
| Goal date | A future date for the entered goal weight. | The average pace and constant intake change required by the model. | A desired date does not make the required plan appropriate. |
| Staged goal | A nearer 5% to 10% change, followed by reassessment. | A shorter, easier-to-review planning window. | A second stage needs new measurements and context. |
| Official NIDDK planner | Detailed diet, activity and time inputs. | The maintained official interface and expert-mode options. | Still needs accurate inputs and professional interpretation when risk is present. |
Why the Timeline Is Not a Forecast
The model improves on the fixed 7,700 kcal per kilogram or 3,500 kcal per pound rule by including changing tissue composition, energy expenditure, glycogen, fluid and adaptive thermogenesis. It still does not know what you eat, how closely intake matches the estimate, whether PAL changes, or how illness and medicines affect you.
NIDDK explains that the traditional 3,500-calorie rule overstates long-term loss because the body responds over time. Its Body Weight Planner is the official implementation. This page independently implements the equations published in the peer-reviewed appendix, uses fixed public assumptions for carbohydrate and sodium changes, and does not include every official interface or expert-mode option.
Set a Goal You Can Review
A large final target can hide whether the first few months are manageable. NIDDK describes an initial goal of 5% to 10% of starting weight within six months as a realistic reference for many adults with overweight or obesity. This is not a target for every person.
The planner warns when the entered goal exceeds 10% of starting weight. It still calculates when the other general-use checks pass, but the message encourages a staged review. At each stage, reassess measurements, symptoms, hunger, training, medications, food quality and whether the original goal still makes sense.
Pace and Calorie Guardrails
The CDC describes gradual loss of about 1 to 2 pounds per week as more likely to be maintained than faster loss. The calculator withholds a plan when the average required pace exceeds 1% of starting weight per week or 0.91 kg, about 2 lb, per week. These are product guardrails, not universal clinical thresholds.
The tool also withholds the plan when the modelled intake reduction exceeds 30% of estimated current maintenance or the plan intake reaches 1,200 kcal/day or lower. It never silently changes an unsafe-looking input into a different plan. A longer time, a smaller staged goal or professional support may be more appropriate.
Why 1,200 Calories Is a Guardrail
NIDDK's Diabetes Prevention Program material states that eating below 1,200 calories per day is not advised. Current NICE guidance classifies 800 to 1,200 kcal/day as a low-energy diet that should be used only within a supported, nutritionally complete, multicomponent strategy in appropriate services.
The threshold is not a personal prescription or a biological minimum for every adult. It is a conservative limit for an automated public tool. If a calculated milestone reaches it, the planner withholds all calorie and timeline outputs instead of displaying a low number with a small warning.
BMI Checks and Their Limits
The planner calculates current and goal BMI from entered height and weight. It withholds a plan when either BMI is below 18.5. The CDC adult BMI categories classify values below 18.5 as underweight for adults aged 20 and older.
BMI is a screening measure, not a diagnosis. It does not directly measure body fat, muscle, health or the appropriateness of a goal. The tool warns when current BMI is below 25 because a weight-loss target in that range deserves added context. It also flags BMI 40 or higher for qualified support.
Activity Multipliers Are Assumptions
The planner accepts PAL values from 1.40 to 2.50 and defaults to 1.60, matching the range used by the NIDDK interface. PAL is the ratio of total energy expenditure to resting metabolic rate. It is still an assumption unless measured. Work, walking, transport, standing, chores, exercise and day-to-day variation all matter.
Keep PAL consistent with the scenario. Do not select a higher PAL and then add every workout calorie again. If your routine changes during the plan, recalculate. The model holds PAL constant because a separate activity-change intervention is outside this simplified implementation.
How to Review the Plan with Real Data
If tracking weight is appropriate for you, compare several weeks rather than one day. Weigh under similar conditions and use a rolling average. Daily changes often reflect fluid and digestive contents. Food labels, restaurant portions, cooking oils and activity devices also contain error.
If the trend differs from the plan, check consistency before changing intake. Then make a small adjustment and observe again. Recalculate after a meaningful weight or activity change. Stop and seek help for dizziness, fainting, persistent fatigue, menstrual disruption, repeated injuries, bingeing, purging or severe anxiety around food or weight.
When This Planner Is Not Appropriate
This tool is for general adults aged 18 and older. It does not model growth, pregnancy, breastfeeding, frailty, clinical malnutrition, critical illness, major burns, recovery after surgery, tube feeding or eating-disorder treatment. It is not designed for unexplained or unintentional weight loss.
Seek qualified guidance if you use insulin or medicines that can cause low blood glucose, have kidney, liver or heart disease, recently had bariatric surgery, take weight-management medication, follow a medically prescribed diet, or train at high volume. Adults aged 65 and older need added attention to muscle, recovery and nutrient adequacy.
Common Weight-Loss Planning Mistakes
- Choosing a goal date first and assuming the required pace must be suitable.
- Treating a static energy conversion as a guaranteed weight forecast.
- Using one unusually active day to select the whole-week activity factor.
- Adding exercise calories twice.
- Ignoring the lower maintenance estimate near the goal.
- Entering pounds in a kilogram field or treating 5 ft 10 in as 5.10 feet.
- Changing calories after a few noisy scale readings.
- Ignoring symptoms, medications, health conditions or disordered eating.
Calculation Method and Review Sources
Baseline resting energy was checked against the original Mifflin-St Jeor study. The weight path, body-fat regression and constants follow the peer-reviewed Hall model appendix and the Hall adult body-weight dynamics paper. General pace, initial-goal, BMI and low-energy-diet safeguards were reviewed against CDC, NIDDK and NICE guidance.
The tool uses 2.54 centimetres per inch, 0.45359237 kilograms per pound and 4.184 kilojoules per kilocalorie. It uses a 50% carbohydrate assumption, scales sodium with intake, integrates in 0.5-day steps, rounds calorie displays to whole numbers, uses your device date for future milestones and stores nothing outside the current page session.
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Frequently Asked Questions
How does this weight loss planner work?
The planner estimates resting energy, applies PAL, integrates the published Hall fat, lean, glycogen, fluid and adaptation equations, and solves for a constant intake that reaches your goal at the end of the selected window. The timeline is an educational scenario, not a guarantee.
Should I plan by weekly pace or goal date?
Weekly pace starts with the change you select and estimates a date. Goal-date mode starts with the date and shows the required pace. Neither method decides whether the result is right for you, so review all safety messages and personal health factors.
Is the estimated goal date guaranteed?
No. Weight change is not linear. Energy expenditure adapts, activity and intake vary, and fluid changes affect the scale. Use the date as a milestone schedule and review the plan against several weeks of observed data.
Why does the calorie estimate decrease near the goal?
The long-run goal-maintenance estimate is lower than current maintenance because body mass and energy expenditure change. Plan intake remains constant in this scenario. Goal maintenance is solved separately and should not be confused with the lower intake used during the planning window.
Why will the planner not show some results?
The tool withholds the plan during pregnancy or breastfeeding, below BMI 18.5, above its pace or 30% intake-reduction limits, or when modelled plan intake is 1,200 kcal/day or lower. These are general-use safeguards, not medical diagnoses.
Does this use the NIDDK Body Weight Planner model?
It independently implements the adult equations published by Hall and colleagues, including early glycogen, fluid, fat, lean-tissue and adaptation states. It is not the official NIDDK interface, does not imply NIDDK endorsement and omits some expert-mode controls.
What is a realistic first weight-loss goal?
NIDDK describes 5% to 10% of starting weight within six months as a common initial reference for many adults with overweight or obesity. It is not a universal target. Your health, current BMI and clinical needs may support a different goal or no weight-loss goal.
Which resting-energy equation should I choose?
This planner uses Mifflin-St Jeor because the Hall model derives its activity term from a Mifflin baseline. Choose the published male or female coefficient set applicable to the calculation. The equation still estimates rather than measures your resting energy.
How accurate are activity multipliers?
PAL is a rough assumption unless measured. Work, walking, chores, exercise and day-to-day variation all matter. Do not add workout calories again when the selected PAL already includes exercise.
Who should not use this planner?
Do not use it for anyone under 18, pregnancy, breastfeeding, eating-disorder treatment, unintentional weight loss or clinical feeding. Seek professional guidance for major medical conditions, medicines affecting weight or blood glucose, recent surgery, frailty or high-volume training.
Health and Calculation Disclaimer
This planner provides an educational adult calorie-and-time estimate. It does not measure metabolism, prescribe intake, guarantee weight loss, diagnose a condition or replace a physician or registered dietitian. Do not use it for children, pregnancy, breastfeeding, eating-disorder treatment, critical illness or clinical feeding. Seek qualified guidance before a major diet or health change.