Daily planning target
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Enter completed years from 18 to 100.
years
Choose the constant required by the selected published equation.
Accepted range is 100-250 cm or the equivalent in inches.
Accepted range is 30-350 kg or the equivalent in pounds.
The multiplier converts estimated resting expenditure into maintenance calories.
Mifflin-St Jeor is the default when measured body composition is unavailable.
Required for the selected formula; accepted range is 1-69%.
%
Compare maintenance, deficit, surplus, or a custom adjustment.
Accepted range is -30% to +30%.
%
Neutral default: 0%. Accepted range is 0-15%.
%
Changing this refines the macro artifact without changing the selected BMR formula.
Accepted range is 0.8-3.5 grams per kilogram of body weight.
g/kg
Accepted range is 15-50% of the daily target.
%
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Body Composition Calculator Estimate body-fat percentage from tape measurements and compare Navy, RFM, and BMI-age methods with lean-mass and uncertainty context.
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.
Fat-Free Mass Index (FFMI) Calculator Calculate raw or height-normalized FFMI from body-fat or fat-free-mass readings, with sensitivity ranges and goal projections.
Lean Body Mass Calculator Estimate adult lean body mass from height and weight, compare four published equations, or use body-fat routes with FFMI and method-spread checks.

A calorie target is an estimate built in stages. Resting energy comes first, ordinary activity expands it into maintenance energy, and a deficit or surplus moves maintenance toward a goal. Mixing those stages together is a common reason two calorie recommendations appear to disagree.

Basal metabolic rate (BMR) estimates the energy required for basic physiological work at rest. Total daily energy expenditure (TDEE) applies an activity assumption to that resting estimate. Neither value is directly measured here. A laboratory can measure resting energy expenditure under controlled conditions, while a prediction equation uses body measurements or estimated lean mass to approximate it.

Resting estimate
The equation result before an activity multiplier. Age, height, weight, the equation sex constant, and sometimes lean mass determine it.
Maintenance estimate
The resting estimate multiplied by an activity factor, plus any separately declared thermic-effect allowance.
Goal intake
Maintenance adjusted by a chosen percentage. A negative percentage is a deficit; a positive percentage is a surplus.
Macro split
Protein is anchored to body weight, fat to a share of target calories, and carbohydrate receives the remaining calories.

The activity factor usually creates more uncertainty than small differences between equations. A desk job with three weekly workouts can still have modest total activity, while a physically demanding job can raise expenditure even without formal training. Choose a normal, repeatable week rather than the busiest week you can remember.

Body weight is also noisy. Water, sodium, glycogen, digestion, and the menstrual cycle can move a daily weigh-in without reflecting tissue change. Compare a calorie plan with several weeks of consistent intake and average weight, then adjust from the observed trend rather than one day's result.

Health note: energy and macro estimates are educational planning aids, not medical nutrition therapy. Pregnancy, breastfeeding, adolescence, eating-disorder risk, metabolic disease, medication, or rapid unexplained weight change calls for individualized professional guidance.

How to Use This Tool:

Start with the best resting-energy equation your available measurements support, then add planning assumptions one at a time.

  1. Enter Age, Height, Weight, and the published equation's Sex constant. Supported ages are 18–100, heights 100–250 cm, and weights 30–350 kg after conversion.
  2. Choose Resting-energy formula. Mifflin–St Jeor and revised Harris–Benedict use age, height, weight, and sex constants. Katch–McArdle and Cunningham require a body-fat percentage from 1% through 69% because they use estimated lean mass.
  3. Select the Activity assumption that matches ordinary life, not only scheduled exercise. Leave Additional TEF allowance at 0% unless you intentionally want a separate 0–15% addition.
  4. Choose a Goal profile or set a custom adjustment from −30% through +30%. Review maintenance before judging the deficit or surplus.
  5. Select a macro preset or set custom protein and fat anchors. If protein and fat calories exceed the target, reduce one of those anchors before using the macro result.

Interpreting Results:

BMR is the equation's resting estimate, not a recommended intake. Maintenance calories are the more relevant starting point for a stable-weight plan. Target calories apply the selected goal percentage to maintenance, so every downstream macro gram depends on the activity and goal assumptions.

  • Use the Daily delta to see the planned difference from maintenance. The weekly weight figure is only a static energy equivalent based on 7,700 kcal per kilogram; human weight change is dynamic.
  • Compare several weeks of average weight and logged intake. If the trend consistently differs from the estimate, observed maintenance is stronger personal evidence than another equation switch.
  • A macro plan is mathematically balanced when protein and fat leave non-negative calories for carbohydrate. That does not establish micronutrient quality, meal timing, food tolerance, or clinical suitability.

Technical Details:

All height inputs are converted to centimetres and all weight inputs to kilograms. Body-fat equations first estimate lean mass. The complete energy chain keeps full numeric precision, while displayed values are formatted for reading.

Formula Core

The four resting-energy choices use the following equations in kcal/day. In the formulas, W is kilograms, H is centimetres, A is completed years, and L is lean mass in kilograms.

EquationPublished pathFormula
Mifflin–St JeorMale constantBMR=10W+6.25H−5A+5
Mifflin–St JeorFemale constantBMR=10W+6.25H−5A−161
Revised Harris–BenedictMale constantBMR=88.362+13.397W+4.799H−5.677A
Revised Harris–BenedictFemale constantBMR=447.593+9.247W+3.098H−4.330A
Katch–McArdleLean massBMR=370+21.6L
CunninghamLean massBMR=500+22L
L=W×1−BF100

Activity, additional thermic effect, and the goal percentage form the next stage:

Maintenance=BMR×activity×1+TEF100
Target=Maintenance×1+Goal100

A 30-year-old on the male Mifflin path at 75 kg and 175 cm gives 1,698.75 kcal/day. At activity factor 1.55 with no added TEF, maintenance is 2,633.06 kcal/day. A −15% goal gives 2,238.10 kcal/day and a −394.96 kcal/day delta.

Rule Core

AssumptionAvailable valuesEffect
Activity factor1.2, 1.375, 1.55, 1.725, or 1.9Multiplies BMR to produce base TDEE.
Goal profiles0%, −10%, −15%, −20%, +8%, or +15%; custom −30% to +30%Multiplies maintenance to produce target calories.
Weekly energy equivalentDaily delta × 7 ÷ 7,700Reports a static kg/week equivalent, not a dynamic forecast.

Protein grams equal body weight multiplied by the selected g/kg anchor. Protein calories use 4 kcal/g. Fat calories equal target calories multiplied by the selected 15–50% share, and fat grams use 9 kcal/g. Carbohydrate receives the remaining calories at 4 kcal/g. A negative remainder is rejected instead of reporting impossible carbohydrate grams.

Accuracy Notes:

Prediction equations describe average relationships in their source populations. Individual error can be meaningful, especially when body composition, illness, athletic training, or measurement conditions differ from those populations.

  • The activity factors, goal percentages, optional TEF addition, 7,700 kcal/kg equivalent, and macro presets are planning assumptions, not physiological laws.
  • Katch–McArdle and Cunningham inherit the error of the entered body-fat percentage because lean mass is derived from it.
  • Energy needs can change during a diet. Use repeatable intake records and weight averages to recalibrate rather than treating the first estimate as permanent.
  • Seek a clinician or registered dietitian for medical conditions, restrictive dieting, pregnancy, breastfeeding, or symptoms suggesting inadequate energy intake.

References: