How Calorix calculates your calorie target and macros

Your Calorix calorie target isn’t a mystery number. It comes from published equations plus a few documented safety rules, and the same goals engine runs in the app and in the calculators on this site. Here’s every step, with two worked examples you can check yourself.

As the Dietary Guidelines for Americans, 2020–2025 note, calorie needs are estimates, and body weight is the best way to judge intake against needs. Your trend is the real test.

Step 1: estimate your BMR

For adults, Calorix estimates your basal metabolic rate (BMR), the energy your body uses at rest, with the Mifflin-St Jeor equation:

BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + s
s = +5 (male), −161 (female), −78 (other)

The −78 for “other” is the midpoint of the two published constants, a documented Calorix choice. The age term reflects that BMR falls with age, which is why calorie needs generally decrease as adults get older, according to the Dietary Guidelines.

The equation was developed from 498 healthy adults aged 19 to 78, with and without obesity, using indirect calorimetry (Mifflin et al., 1990). Strictly speaking, it predicts resting energy expenditure, which most apps call BMR. A systematic review of the four most commonly used equations found it the most reliable, predicting resting metabolic rate within 10% of measured values in more people than any other, though errors for individuals can still be meaningful (Frankenfield et al., 2005).

Step 2: multiply by an activity factor

Total daily energy expenditure (TDEE) adds the energy you spend moving. Calorix multiplies BMR by one of five standard activity factors widely used with BMR equations:

With the BMR from example A below, the activity choice alone moves the estimate by more than 1,200 kcal a day. These factors are conventions, not measurements, so let your trend show whether your level fits. You can try it in the TDEE calculator.

Step 3: set the target from your goal and pace

Calorix adjusts TDEE by the energy implied by your weekly pace, in kg:

Lose:     target = TDEE − pace × 7,700 ÷ 7
Gain:     target = TDEE + pace × 7,700 ÷ 7
Maintain: target = TDEE

The 7,700 kcal per kg figure is roughly the metric version of the familiar 3,500 kcal per pound rule. A “lose” goal whose goal weight isn’t at least 0.1 kg below your current weight counts as maintenance, and the same goes for “gain”. The calorie deficit calculator runs this step with your numbers.

Pace limits. Pace is capped at 1% of your body weight per week, with a warning above 0.75%. At 80 kg, that’s a cap of 0.8 kg and a warning above 0.6 kg. This cap is what keeps a plan from turning into a crash diet. For context, the CDC notes that people who lose about 1 to 2 pounds (roughly 0.5 to 0.9 kg) a week are more likely to keep the weight off than people who lose it faster.

The limits of the 7,700 rule. It ignores how the body adapts as weight changes, including shifts in resting metabolic rate and in the energy cost of activity (Hall et al., 2011). Researchers who compared its predictions with seven closely supervised weight-loss experiments warned that it overestimates actual weight loss (Thomas et al., 2013). Calorix uses it as a starting point and says plainly that real progress usually slows.

Step 4: apply the calorie minimum

No target goes below 1,200 kcal a day for women, 1,500 for men or 1,350 for “other”, the midpoint of the two. The 1,200 and 1,500 values are the bottom of the ranges in the 2013 AHA/ACC/TOS obesity guideline, developed with the NIH’s National Heart, Lung, and Blood Institute, which lists 1,200–1,500 kcal a day for women and 1,500–1,800 for men as one way to prescribe a weight-loss diet (Jensen et al., 2014).

The minimum applies to every goal and only ever raises a target. When it raises a weight-loss target, Calorix recalculates your pace from the deficit that’s left, (TDEE − target) × 7 ÷ 7,700, and bases your goal date on it.

Step 5: split calories into protein, fat and carbs

Grams convert to calories with the general factors used on US nutrition labels: 4 kcal per gram for protein and carbohydrate, and 9 for fat (21 CFR 101.9).

Protein

Protein is 1.6 g per kg of goal-adjusted weight, or 2.0 g/kg when you’re losing weight, capped at 2.2 g per kg of current weight and at 35% of your calories. Goal-adjusted weight is your goal weight when you’re losing toward a lower goal or gaining toward a higher one, and your current weight otherwise. That keeps targets sensible for people with a lot of weight to lose: at 120 kg with a 90 kg goal, the calculation starts from 2.0 × 90 = 180 g rather than 240 g.

• 1.6 g/kg is the top of the 1.2–1.6 g/kg protein goal in the Dietary Guidelines for Americans, 2025–2030, and about where a meta-analysis of 49 trials found extra protein stopped adding to strength-training gains in fat-free mass (Morton et al., 2018).
• 2.0 g/kg when losing sits slightly above that range. In a meta-analysis of 24 trials, higher-protein, calorie-restricted diets helped limit the loss of fat-free mass (Wycherley et al., 2012). It’s still the high end of common advice: a 2025 joint advisory on GLP-1 therapy suggests avoiding prolonged intakes at or above 2 g/kg per day (Mozaffarian et al., 2025). A goal weight below your current weight brings it under 2.0 g per kg of current weight. If you take a GLP-1 medication, see GLP-1 medications and protein.
• 35% of calories is the top of the adult Acceptable Macronutrient Distribution Range for protein, 10–35%, listed in the 2020–2025 Dietary Guidelines.

If you have kidney disease, are pregnant or breastfeeding, or have a protein target from your clinician, follow their advice. More in protein targets explained and the protein calculator.

Fat and carbs

• Fat is 30% of calories, or 70% on keto.
• Carbs are the remainder, capped at 30 g on keto and at the lower of 130 g or 26% of calories on low carb, with any excess going to fat.

Try your split in the macro calculator.

Fiber, water and rounding

• Fiber is 14 g per 1,000 kcal, the basis of the Adequate Intake for fiber in the Institute of Medicine’s 2005 report and the fiber goal used in the 2020–2025 Dietary Guidelines.
• Water is 33 ml per kg of body weight, a simple rule of thumb. Needs change with heat, activity and health, and a fluid limit from your doctor comes first.
• Rounding: calories round to the nearest 10 kcal, grams to the nearest whole gram (halves round up) and water to the nearest 50 ml.

Worked example A: a standard weight-loss target

A man, 30, 180 cm and 80 kg, moderately active, losing 0.5 kg a week with the default split. That pace is under both the 0.6 kg warning and the 0.8 kg cap, and the 1,500 kcal minimum doesn’t come into play.

With a 75 kg goal weight, protein becomes 150 g and carbs 237 g, and the straight-line projection to 75 kg is 70 days.

Worked example B: when the calorie minimum steps in

A woman, 25, 165 cm and 60 kg, sedentary, with a 55 kg goal, asks to lose 1.0 kg a week:

1. Pace: capped at 0.6 kg (1% of 60 kg), still above the 0.45 kg warning level, so Calorix flags it.
2. BMR: 10 × 60 + 6.25 × 165 − 5 × 25 − 161 = 1,345.25 kcal.
3. TDEE: 1,345.25 × 1.2 = 1,614.3 kcal.
4. Raw target: 1,614.3 − 660 (0.6 × 7,700 ÷ 7), about 954 kcal.
5. Minimum: that’s below the 1,200 kcal minimum for women, so the target becomes 1,200 kcal.
6. Real pace: (1,614.3 − 1,200) × 7 ÷ 7,700, about 0.38 kg a week, which puts the projection to 55 kg at 93 days.
7. Macros: protein would be 2.0 × 55 = 110 g, but the 35% cap (420 kcal) brings it to 105 g. Fat is 40 g, carbs 105 g, fiber 17 g and water 2,000 ml.

Instead of a very low target, you get a realistic one and an honest projection.

Your goal date, and how targets update

Your goal date is the weight still to change, divided by your real weekly pace, times seven, rounded up to whole days. That straight line is a planning tool, not a prediction: in Hall’s model, the response to a lasting change in intake is slow, with about half of the eventual change taking around a year. Expect the curve to flatten, and watch the smoothed trend in your weight log.

Calorix recalculates your targets whenever your weight or goal changes, using weigh-ins you log or that it reads from Apple Health. In the adult equation, each kilogram changes BMR by 10 kcal, and weight also drives your protein and water targets.

If you’re under 18

Calorix’s minimum age is 13, and it never sets a calorie deficit for anyone under 18: a “lose” goal becomes maintenance, and the app suggests talking to a doctor. Teens 13 to 18 also get a different energy equation, the National Academies’ estimated energy requirement for adolescents, because energy needs rise through adolescence to support growth and development, according to the 2020–2025 Dietary Guidelines. The calculators on this site are designed for adults.

What the formulas can’t know

Equations work on averages and don’t know your medical history. Talk to a doctor or registered dietitian if you have a medical condition or kidney disease, are pregnant or breastfeeding, have a history of disordered eating, or take a GLP-1 or diabetes medication. Otherwise, give the plan a few weeks, watch your trend, and adjust activity or pace if needed.

The bottom line

Your Calorix target is Mifflin-St Jeor BMR × an activity factor, adjusted for your pace, kept at or above a calorie minimum, then split into protein, fat, carbs, fiber and water. Every step is a published equation or a documented rule. Treat it as a well-reasoned first estimate, and let your trend refine it.