How are the calorie and protein targets set?

Calories start from Mifflin-St Jeor BMR × an activity factor (your TDEE), then adjust by −500 kcal for cutting or +300 kcal for bulking. Protein is set per kilogram of bodyweight — highest for cutting (2.2 g/kg) to protect muscle in a deficit, lower for maintenance (1.8 g/kg).

Why is fat a fixed 25% of calories?

25% of total calories sits comfortably inside the 20–35% range most nutrition guidelines consider adequate for hormone production and fat-soluble vitamin absorption, leaving the rest of the budget for protein and carbohydrate.

Should I hit these numbers exactly every day?

No — daily totals naturally vary. Aim for the weekly average to land close to target rather than forcing exact numbers every single day, which tends to be unsustainable and isn't necessary for results.

Macro Calculator

Calculate daily protein, fat and carbohydrate targets in grams from your stats, activity level and goal — cutting, maintaining or bulking.

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Formula: Calories = Mifflin-St Jeor TDEE ± goal adjustment; protein = g/kg bodyweight by goal; fat = 25% of calories; carbs = remainder

Worked examples

30-year-old man, 178 cm, 80 kg, moderately active, cutting
A cutting split uses the highest protein target (2.2 g/kg) to protect lean mass in a deficit.
28-year-old woman, 165 cm, 62 kg, lightly active, maintaining
A maintenance split with calories at TDEE and a moderate 1.8 g/kg protein target.
22-year-old man, 183 cm, 70 kg, active, bulking
A lean-bulk split adds calories above TDEE and leaves more room for carbohydrate to fuel training.

What this calculator does

Macros — protein, fat and carbohydrate — are the three nutrients that make up your calorie intake. This tool takes your stats and a goal (cutting, maintaining, or bulking) and returns a daily calorie target plus a gram breakdown across all three, so you have a concrete plan rather than just a total calorie number.

How the numbers are built

Calories start from your Mifflin-St Jeor basal metabolic rate, multiplied by an activity factor to get your estimated TDEE (Total Daily Energy Expenditure) — the same method used by the TDEE calculator elsewhere in this hub. Your goal then adjusts that baseline: −500 kcal/day for cutting, unchanged for maintaining, +300 kcal/day for a lean bulk.
Protein is set per kilogram of bodyweight, and the target changes with your goal: highest for cutting (2.2 g/kg), to help protect lean mass while in a calorie deficit; moderate for maintenance (1.8 g/kg); and a slightly lower 2.0 g/kg for bulking, since a calorie surplus itself helps preserve and build muscle.
Fat is fixed at 25% of total calories, comfortably inside the 20–35% range most nutrition guidelines treat as adequate for hormone production and absorbing fat-soluble vitamins.
Carbohydrate takes whatever calories remain after protein and fat are accounted for, converted to grams at 4 kcal per gram.

Why goal changes the split, not just the calories

Simply eating more or less at a fixed macro ratio misses an important detail: protein needs don't scale down proportionally with a smaller calorie budget the way fat and carbs can. Keeping protein relatively high during a cut is one of the more consistently supported findings in body-composition research for preserving muscle while losing fat, which is why this calculator raises the per-kilogram protein target for cutting rather than just shrinking every macro by the same percentage.

How to use the result

Treat these numbers as a sensible, evidence-informed starting point rather than a fixed prescription — an individualized plan from a coach or dietitian may reasonably use different splits based on training volume, food preferences, or specific goals this general calculator can't see. Aim for your weekly average to land close to target rather than hitting the exact numbers every single day, which is rarely necessary and often unsustainable. If you want to fine-tune protein specifically, the protein intake calculator elsewhere in this hub offers goal-specific targets in more detail.

Limits

The underlying BMR and TDEE estimates carry the same ±10–15% uncertainty as any population formula, and the fat/protein/carb split here is one reasonable default among many defensible approaches — not the only correct one. This tool provides general nutrition information, not individualized dietary or medical advice; consult a registered dietitian for a plan tailored to your specific health situation.

Frequently asked questions

How are the calorie and protein targets set?: Calories start from Mifflin-St Jeor BMR × an activity factor (your TDEE), then adjust by −500 kcal for cutting or +300 kcal for bulking. Protein is set per kilogram of bodyweight — highest for cutting (2.2 g/kg) to protect muscle in a deficit, lower for maintenance (1.8 g/kg).
Why is fat a fixed 25% of calories?: 25% of total calories sits comfortably inside the 20–35% range most nutrition guidelines consider adequate for hormone production and fat-soluble vitamin absorption, leaving the rest of the budget for protein and carbohydrate.
What if the numbers don't match my diet coach's plan?: This is a general-purpose starting point using population-level protein targets; an individualized plan may reasonably use different splits based on training volume, body composition or dietary preference. Treat this as a sensible default, not a fixed prescription.
Should I hit these numbers exactly every day?: No — daily totals naturally vary. Aim for the weekly average to land close to target rather than forcing exact numbers every single day, which tends to be unsustainable and isn't necessary for results.

These calculators give general estimates from published formulas. They are not medical advice and do not account for your individual health; talk to a qualified professional before changing your diet or training.