How MacroLab calculates starting calorie and macro targets
This page documents the public calculator as shipped: inputs, equations, planning rules, safety limits, and known uncertainty.
Last updated July 30, 2026 · Author: MacroLab product team · Corrections: hello@g10app.com
1. Scope and eligibility
The calculator is an educational estimate for adults age 18 to 100. It is not intended for pregnancy or breastfeeding. People with a medical condition, medication affecting weight or metabolism, or an eating-disorder history should use individualized guidance from a physician or registered dietitian.
Inputs are sex used by the published equation, age, height, weight, usual activity, goal, and an optional weekly planning pace.
2. Resting energy
The calculator uses the Mifflin–St Jeor equation, which technically estimates resting energy expenditure. It is often called BMR in consumer tools.
Male coefficient: 10W + 6.25H − 5A + 5
Female coefficient: 10W + 6.25H − 5A − 161
W = kilograms · H = centimeters · A = years
The coefficients come from the populations studied and do not define gender identity. The estimate may be less applicable when the coefficient does not reflect a person's physiology or medical treatment.
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.
3. Estimated maintenance energy
Resting energy is multiplied by one activity factor. These broad categories combine everyday movement and exercise. They are planning assumptions rather than a direct measurement of energy expenditure.
| Selected activity | Factor |
|---|---|
| Mostly seated, little exercise | 1.200 |
| Light activity, 1–3 days/week | 1.375 |
| Moderate activity, 3–5 days/week | 1.550 |
| Hard activity, 6–7 days/week | 1.725 |
| Very hard training or physical work | 1.900 |
4. Goal adjustment and safety limits
For loss or gain, the selected weekly percentage is converted to kilograms per week. The planning conversion uses 7700 kcal per kilogram and divides by seven days. This is a simplification; human weight change is dynamic and does not follow a fixed conversion indefinitely.
Loss pace is capped at 1% of body weight per week. Gain pace is capped at 0.5% for the starting estimate. A weight-loss target never falls below the larger of 1.1 times estimated resting energy or 1500 kcal for the male coefficient and 1200 kcal for the female coefficient. A binding floor is rounded upward to 25 kcal. If that floor meets or exceeds estimated maintenance, the calculator returns no automated deficit instead of reversing the goal.
Hall KD et al. Quantification of the effect of energy imbalance on bodyweight.
5. Macro and water planning targets
Default protein is 2.0 g/kg for weight loss, 1.8 g/kg for weight gain, and 1.6 g/kg for maintenance. Fat starts at 0.8, 1.0, and 0.9 g/kg respectively, with a minimum of 40 g and 0.5 g/kg. Carbohydrate receives remaining planned energy with a 50 g minimum. Water starts at 35 mL/kg, rounded to 250 mL and bounded between 1.5 and 6 liters.
These are app planning defaults, not universally optimal prescriptions. The National Academies' adult acceptable ranges span 10–35% of energy from protein, 20–35% from fat, and 45–65% from carbohydrate.
If the weight-based macro minimums cannot fit within the calorie target, the public calculator returns an individualized-planning message instead of displaying calorie and macro values that conflict.
National Academies. Dietary Reference Intakes for macronutrients.
6. What happens after the estimate
MacroLab treats the result as a starting point. With sufficient logged intake and weight data, the product can compare predicted expenditure with observed trends and update future targets. Short-term changes remain noisy, so no single weigh-in should be interpreted as a metabolic measurement.
Read why calorie estimates change, or return to the calculator.