Purpose and steps
Estimates maintenance calories with Mifflin–St Jeor and an activity multiplier, then adds the selected surplus and shows a common protein range for active adults.
- Choose units and use the pre-pregnancy, resting or current measurements requested by the tool; keep observation dates consistent.
- Prepare Sex used by the equation, Age, Weight, Height, Daily activity level, Calorie surplus. Defaults demonstrate the model rather than your personal circumstances.
- Check the headline result and its components. A key interpretation for this tool is: Track strength, training quality, and weight trend together.
- Compare the baseline with a changed scenario: A smaller surplus generally limits unnecessary fat gain better than a large surplus.
Input reference and units
These values reproduce the model’s demonstration. Replace them with your own records or measurements; they are not recommended targets.
On a small screen, swipe the table horizontally to see all columns.
| Parameter | Demonstration value | How to enter it |
|---|---|---|
| Sex used by the equation | Female | Use the definition shown in the field label; keep this assumption consistent when comparing scenarios. |
| Age | 30 years | Use years here. The model converts to months when the payment schedule requires it. |
| Weight | 70 kg | Use the definition shown in the field label; keep this assumption consistent when comparing scenarios. |
| Height | 170 cm | Use the definition shown in the field label; keep this assumption consistent when comparing scenarios. |
| Daily activity level | Moderately active (3–5 days/week) | Use the definition shown in the field label; keep this assumption consistent when comparing scenarios. |
| Calorie surplus | Moderate +10% | Use the definition shown in the field label; keep this assumption consistent when comparing scenarios. |
Model-specific method
How this calculator produces its result
Maintenance = Mifflin–St Jeor BMR × activity factor. Gain target = maintenance × (1 + selected surplus). Protein range is calculated from body weight.
Energy bookkeeping and weighted allocation
Energy allocation is a weighted sum because grams of protein, carbohydrate and fat have different modeled energy densities. Subtract the energy already assigned before converting the remainder into another nutrient. Dividing remaining calories by four rather than nine would miscalculate fat grams.
A static deficit or surplus is a budgeting estimate rather than a linear prediction of body-weight change. Expenditure can adapt, measurement is imperfect and changes in water and lean tissue affect weight. Activity factors can already include exercise; adding it again may double-count energy use.
TDEE ≈ estimated resting energy × activity factor Energy from macros = 4 × protein grams + 4 × carb grams + 9 × fat grams Planned balance = intake − estimated expenditure
- kcal: energy, not food mass
- g: grams of the selected macronutrient
- Activity factor: empirical multiplier, not measured exercise energy
- Balance: model estimate over the specified period
Worked example
If estimated maintenance is 2,250 kcal/day, a 10% surplus gives about 2,475 kcal/day. At 70 kg, the displayed 1.4–2.0 g/kg protein reference is about 98–140 g/day.
Reproduce the default scenario
This is a separate example, calculated using the exact engine on the tool page and the defaults in the input reference above. Health examples use metric units. Displayed rounding may differ from intermediate precision.
- Daily muscle-gain calorie target
- 2,475 kcal/day
- Estimated maintenance
- 2,250 kcal/day
- Daily calorie surplus
- 225 kcal/day
- Protein reference range
- 98–140 g/day
Reading results without overstating them
- Track strength, training quality, and weight trend together.
- A smaller surplus generally limits unnecessary fat gain better than a large surplus.
Assumptions and exclusions
- Training age, program quality, sleep, and genetics affect the useful surplus.
- The calculation does not design a resistance-training or meal plan.
Sources and content notes
Toolify describes the implemented algorithm and its assumptions. Sources below support the topic or applicable rules; they do not endorse this calculator. Examples are illustrative, and published rules take precedence over simplified estimates.
- Original Mifflin–St Jeor resting energy equation study
- International Society of Sports Nutrition: Protein and Exercise
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