Calculation overview
The calculators convert metric, US, or UK stone/pound measurements to kilograms and centimeters before applying the equations. They estimate resting energy, apply an activity factor to produce a maintenance midpoint, apply an optional percentage goal adjustment, and then build macro and weekly-planning ranges around the result.
No equation measures metabolism. Indirect calorimetry, careful longitudinal observation, and professional assessment answer different questions and may be more suitable in clinical or athletic contexts.
Resting-energy equations
Mifflin–St Jeor
This is the default because a systematic review found it comparatively reliable for predicting resting metabolic rate in non-obese and obese adults, while also reporting meaningful individual error. The equations are:
Male constant: BMR = 10W + 6.25H − 5A + 5
Female constant: BMR = 10W + 6.25H − 5A − 161
W is kilograms, H is centimeters, and A is years. The sex input reflects how the published model was constructed; it does not represent gender identity. The live result also shows the revised Harris–Benedict equation as a comparison so users can see model disagreement; it does not drive the target unless explicitly added as a selectable formula in a future release.
Katch–McArdle
When body-fat percentage is reasonably known, the optional equation estimates resting energy from lean mass: BMR = 370 + 21.6 × lean mass in kilograms. A poor body-fat estimate can make this less useful than the default.
Activity estimate
Many calculators ask users to choose labels such as “light” or “moderate.” Those labels are easy to interpret inconsistently. Calorie Method instead starts at 1.20 and adds conservative increments for training frequency, approximate steps, and occupational movement.
| Input | Choices | Contribution |
|---|---|---|
| Training | None to 5+ sessions | 0.00 to 0.24 |
| Daily steps | Under 3,000 to 10,000+ | 0.00 to 0.16 |
| Workday movement | Seated to physical | 0.00 to 0.18 |
The maximum factor is capped at 1.90. These increments are a transparent product heuristic, not a clinically validated activity instrument. Users should regard activity as the estimate's most adjustable assumption.
Walking, treadmill, and steps estimates
The activity calculator converts speed to metres per minute and grade percentage to a decimal. For steady-state walking it uses VO₂ = 3.5 + 0.1 × speed + 1.8 × speed × grade. For running it uses VO₂ = 3.5 + 0.2 × speed + 0.9 × speed × grade. Gross kcal/min = VO₂ × kg ÷ 200. Net activity kcal subtracts the 3.5 ml/kg/min resting component before applying the same conversion.
The equations do not model handrail support, changing pace, outdoor terrain, wind, individual economy, or treadmill calibration. Walking is limited to 1.9–8 km/h and running to 8–20 km/h to avoid presenting implausible mode combinations. The displayed ±20% band is a Calorie Method uncertainty reminder, not a confidence interval.
For an inverse step estimate, duration = target gross kcal ÷ gross kcal/min and steps = duration × user-entered cadence. Calories and steps are not true interchangeable units; cadence changes step count while speed, grade, and body mass drive the energy equation. Session calories are never automatically added to TDEE because the daily activity factor may already include them.
Why the result includes a range
The displayed practical range is the goal midpoint plus or minus 8% of estimated maintenance. It is an honest visual reminder that the midpoint is uncertain. It is not a statistical confidence interval, safe-intake range, or promise that true maintenance lies inside it.
Goal adjustments, specialized tools, and warnings
The general calculator changes maintenance by 10% or 15%, with custom settings from 5–20%. The deficit calculator compares 5%, 10%, 15%, and 20%. The weight-gain calculator compares 5%, 10%, and 15%. All of these percentages are Calorie Method planning heuristics—not values validated by the resting-energy studies—and cannot predict an exact rate or goal date.
The calculator does not silently replace a result with a universal calorie floor. Instead, the deficit page visibly warns when a target is below estimated resting energy or reaches a 20% deficit. The gain page cautions at 15% because more surplus does not guarantee faster muscle gain.
Gain mode shows protein context from 1.4–2.0 g/kg/day for general exercising adults and 1.6–2.0 g/kg/day for lean-bulk mode. The ISSN position stand provides broad sports-protein context; the mode boundaries are product choices, not individualized prescriptions. Its illustrative weekly allocation uses relative weights of 1.05, 0.97, 1.05, 0.97, 1.05, 0.95, and 0.96. They sum to 7.00, and final-day rounding is reconciled so the displayed days equal the rounded daily target multiplied by seven.
Manual food and meal scaling
The food calculator embeds no food-composition records. It scales values entered from a verified record or label using: serving grams × quantity ÷ basis grams. Each nutrient per basis is multiplied by that factor, then item values are summed. The source type and record or label identifier remain visible. This arithmetic does not correct label rounding, choose a food record, calculate recipe yield, or infer nutrients from a food name.
Recipe yield and serving calculation
The recipe calculator extends manual food scaling. Each ingredient nutrient equals its value per basis multiplied by ingredient grams and divided by basis grams. Ingredient values are summed. Per-serving values divide totals by serving count; per-100-gram values multiply totals by 100 and divide by measured final cooked yield.
Measured yield changes concentration but this implementation applies no nutrient-retention factor. It does not infer evaporation, absorbed water, drained fat, discarded liquid, bones, or vitamin losses. Users must select preparation-specific source records and account for measurable discarded material themselves. Values retain source type, record or label ID, and public URL when one exists.
Macro starting ranges
Protein and fat are calculated from body weight using ranges selected by the balanced, higher-protein, or lower-carbohydrate preference. Remaining calories are assigned to carbohydrate. This is more adaptive than a universal percentage split, but the ranges have not yet received registered-dietitian review and are not clinical prescriptions.
Observed-trend calibration
The optional calibration uses: observed maintenance ≈ average intake − (weight change in kg × 7,700 ÷ days). Negative weight change therefore raises the estimated maintenance above intake. This rough arithmetic is very sensitive to water, glycogen, digestive content, and intake-reporting error. Use at least 14–21 days and interpret it alongside—not instead of—the equation result.
Who should not rely on this tool
It is for generally healthy adults. It is not designed for minors, pregnancy, breastfeeding, eating-disorder treatment, medical nutrition therapy, serious illness, or clinician-supervised diets. Medication, disability, menopause, extreme body composition, and high-level sport may also require individualized assessment.
Primary references
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals.
- Frankenfield D et al. Comparison of predictive equations for resting metabolic rate.
- NIDDK research behind the Body Weight Planner.
- CDC guidance on gradual, sustainable weight management.
For a source-by-source account of what affects code, what provides context, and what remains a Calorie Method heuristic, see the evidence and data-source library.