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Opening pace {{ resultsReady ? formatWeeklyChange(computation.values.opening_weekly_change_kg) : '—' }} Goal date {{ resultsReady ? formatDate(computation.values.goal_date) : '—' }} BMI {{ resultsReady ? `${formatNumber(computation.values.current_bmi, 1)} → ${formatNumber(computation.values.goal_bmi, 1)}` : '—' }}
Adults age 20 to 100.
This selection controls an equation constant; it is not a complete description of identity or physiology.
Changing units converts the displayed quantity instead of reinterpreting it.
Supported normalized range: 35 to 350 kg.
The planner handles loss, maintenance, and gain scenarios.
Both modes use exact calendar days in the canonical model.
Dates are evaluated as calendar days, not elapsed local-clock hours.
The resolved plan must be between 7 and 730 days.
A date at or before the start is rejected.
Choose the routine you already sustain during most weeks.
The preset uses 1,200 kcal/day with the female formula and 1,500 kcal/day with the male formula.
Accepted planner range: 600 to 4,000 kcal/day.
kcal/day
This only changes supporting artifact density; the default weekly setting is neutral.
Plan brief
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Calculation method:
Mifflin-St Jeor estimates resting energy, activity estimates TDEE, and the runway recalculates TDEE after each simulated day.
daily Δkg = (TDEE at current simulated weight − intake) ÷ 7,700
Review before using this estimate:
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This browser-local model is a planning estimate, not a medical prescription. Calibrate it against a multi-week measured trend and qualified advice when health risks or symptoms are involved.

The chart renderer is unavailable. The same checkpoints remain available in the runway schedule.

CheckpointDateWeightBMITDEECopy
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Weight-for-Age Percentile Calculator Calculate a child's weight-for-age percentile from WHO or CDC reference data with corrected-age handling and clear screening limits.
Body Mass Index (BMI) Calculator Calculate adult BMI from height and weight, compare three reference systems, and add waist-to-height and healthy-band weight context.
BMR & TDEE Calculator Estimate BMR and TDEE, compare resting-energy formulas, and turn activity and goal assumptions into calorie and macro targets.
Body Metrics Calculator Compare adult BMI and waist ratios with three body-fat estimates, derived fat and lean mass plus BSA and method-spread warnings.

Body weight rarely changes along a perfectly straight line. Food and fluid shifts can move the scale from day to day, while a lasting trend develops from energy intake, activity, body size, and time. A useful plan therefore needs both a destination and a pace that can be checked against real measurements.

Calorie planning usually starts with resting energy expenditure, the energy needed for basic body functions at rest. An activity factor turns that estimate into total daily energy expenditure (TDEE). Eating below TDEE creates a modeled deficit; eating above it creates a modeled surplus. As weight changes, energy needs also change, so a fixed daily intake can produce a faster pace at the beginning and a slower pace near the end.

Planning target
A daily calorie estimate intended to model a requested weight and time window, not prescribe a diet.
Runway
A day-by-day projection that recalculates TDEE as modeled weight changes.
Pace
The modeled weekly change near the start and finish. A large opening deficit deserves more caution than a slower, longer plan.

Body mass index (BMI) adds broad weight-for-height context, but it is a screening measure rather than a diagnosis. Medication, pregnancy, breastfeeding, illness, eating-disorder history, athletic training, and changes in body composition can all make a general model unsuitable or incomplete. Adults with symptoms, an underweight goal, or a major planned change should involve a qualified health professional.

The largest practical mistake is treating one estimate as a promise. Energy equations describe group averages, activity categories are broad, and the model does not know an individual's absorption, adaptive metabolism, or changing routine. Use a multi-week trend to calibrate the plan instead of reacting to a single weigh-in.

How to Use This Tool:

Define the adult starting measurements and goal window before choosing activity and safety-floor assumptions.

  1. Enter an adult age, height, current weight, and goal weight. Choose the female or male Formula sex constant that applies to the resting-energy equation.
  2. Set the goal by a duration or target date. The resolved window must be from 7 through 730 calendar days; months use 30.4375 days before the total is rounded to a whole day.
  3. Choose the activity level that best matches an already sustained routine. Selecting an aspirational level can overstate TDEE and the calorie target.
  4. Keep the preset Planning floor, enter a clinician-guided custom floor, or deliberately select no floor. A floor can extend the finish when the requested loss pace would require a lower mathematical intake.
  5. Compare the daily target, opening and finishing pace, projected end weight, BMI context, and warnings. Change the goal or timing when the plan is floor-limited, unusually fast, or outside the intended adult screening range.

Interpreting Results:

The daily target is the intake that the model applies every simulated day. On track means the projected end weight is within 0.1 kg of the goal. Later finish or Floor limited means the displayed intake does not reach the requested goal inside the chosen window.

  • Opening pace above 2 lb per week triggers a rapid-loss warning; it is a planning signal, not proof that the same pace will occur.
  • A goal BMI below 18.5 triggers an underweight warning. BMI does not establish an individual's health status.
  • The runway is most useful as a trend. Compare it with consistent weigh-ins over several weeks, then revisit activity and intake assumptions if the measured trend differs materially.

Technical Details:

The model combines a published resting-energy equation with a declared adaptive planning runway. Height and weight are normalized to centimetres and kilograms, dates become exact calendar-day counts, and full precision is retained throughout the simulation.

Formula Core:

Mifflin–St Jeor estimates basal metabolic rate (BMR), then an activity factor estimates starting TDEE.

BMR=10W+6.25H−5A+s TDEE=BMR×f

Here, W is weight in kilograms, H is height in centimetres, A is age in years, and s is +5 for the male formula or −161 for the female formula. The activity factor f is 1.200, 1.375, 1.550, 1.725, or 1.900 from sedentary through extra active.

For example, an 80 kg, 175 cm, 35-year-old using the male constant has a BMR of 1,723.75 kcal/day. With the moderate factor of 1.55, starting TDEE is about 2,672 kcal/day.

Each simulated day updates weight from the difference between that day's TDEE and the fixed intake target C.

Wd+1=max(15,Wd−TDEEd−C7700)

The 7,700 kcal/kg value is a static planning assumption, not a body-composition model. A 60-iteration binary search finds the fixed intake that would reach the requested weight in the chosen number of days. For loss plans, the selected calorie floor is applied after that search, and the runway is recalculated with the higher intake.

BMI=W(H÷100)2

Rule Core:

RuleExact behaviorPractical meaning
Adult domainAge 20–100; normalized height 120–230 cm; each weight 35–350 kgValues outside these ranges are rejected.
Preset floor1,200 kcal/day with the female equation constant; 1,500 kcal/day with the male constantApplied only to loss when the raw target is lower.
Goal reachedAbsolute projected gap ≤ 0.1 kgA larger gap changes the status to a later finish.
Rapid lossOpening modeled loss > 2 lb/weekTriggers a pace warning.
Underweight screenBMI < 18.5Triggers a warning for a current loss scenario or underweight goal.
Checkpoint spacingEvery 7 or 30 days, plus the final dayChanges table and chart density, not the calculation.

Accuracy and Safety Notes:

This is a browser-local planning estimate, not medical advice or a prescription. The activity multipliers and 7,700 kcal/kg assumption simplify physiology, while BMI is only a screening measure. Do not use the result for children, pregnancy or breastfeeding, eating-disorder care, or a medical condition without qualified guidance.

No entered measurements are sent to a calculation service. A saved or shared link can still contain selected values, so review it before sending it to someone else.

References: