1,618
kcal/day
2,507
kcal/day
2,507
kcal/day
188
g/day
251
g/day
84
g/day
2.69
g/kg/day
3.58
g/kg/day
1.19
g/kg/day
1,618
kcal/day
2,507
kcal/day
2,507
kcal/day
188
g/day
251
g/day
84
g/day
2.69
g/kg/day
3.58
g/kg/day
1.19
g/kg/day
The Macro Calculator uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE), then distributes your target calories across protein, carbohydrates, and fat based on your chosen macro split. Whether you are cutting, maintaining, or building muscle, understanding your macros is the foundation of evidence-based nutrition.
Macronutrients — protein, carbohydrates, and fat — are the three categories of nutrients that provide energy. Protein and carbohydrates each yield 4 kcal per gram, while fat yields 9 kcal per gram. The Mifflin-St Jeor equation (1990) is considered the most accurate predictor of resting energy expenditure in the general population, validated against indirect calorimetry across multiple studies. For men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5. For women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161.
TDEE is obtained by multiplying BMR by an activity factor: sedentary (1.2), lightly active (1.375), moderately active (1.55), very active (1.725), or extra active (1.9). Your target calories are then adjusted based on your goal — a 500 kcal deficit for weight loss (approximately 0.5 kg/week), maintenance at TDEE, or a 300 kcal surplus for lean mass gain.
The calculator offers four evidence-based macro splits: Balanced (40C/30P/30F) — suitable for general fitness and weight maintenance; Low Carb (20C/40P/40F) — useful for insulin resistance, reducing blood sugar spikes; High Protein (40C/40P/20F) — maximizes muscle protein synthesis for athletes and bodybuilders; Ketogenic (5C/25P/70F) — very low carbohydrate diet for metabolic and weight loss purposes. Protein is prioritized at a minimum of 1.6–2.2g/kg body weight for active individuals to support muscle retention and satiety.
Use this calculator as a starting point. Individual variation in metabolic rate, gut microbiome, hormones, and non-exercise activity thermogenesis (NEAT) means that your actual caloric needs may differ by 10–20% from the estimate. Track your weight trend over 2–3 weeks and adjust intake accordingly.
BMR (Mifflin-St Jeor): Male: 10W + 6.25H − 5A + 5; Female: 10W + 6.25H − 5A − 161 (W=kg, H=cm, A=years). TDEE = BMR × Activity Factor. Target = TDEE − 500 (lose) / TDEE (maintain) / TDEE + 300 (gain). Macros: Protein (g) = Target × protein_ratio / 4; Carbs (g) = Target × carb_ratio / 4; Fat (g) = Target × fat_ratio / 9.
Your BMR is the minimum calories needed at rest. TDEE reflects total daily burn. Target calories are what you should eat to reach your goal. Macro grams tell you exactly how much of each macronutrient to consume. Track with a food diary app and adjust every 2–3 weeks based on actual weight change.
Inputs
Results
BMR = 10×75 + 6.25×178 − 5×28 + 5 = 1814. TDEE = 1814 × 1.55 = 2812. Target = 2812 − 500 = 2312. Protein = 2312×0.30/4 = 173g; Carbs = 2312×0.40/4 = 231g; Fat = 2312×0.30/9 = 77g.
Inputs
Results
BMR = 10×60 + 6.25×163 − 5×35 − 161 = 1380. TDEE = 1380 × 1.375 = 1898. High Protein 40/40/20: Protein = 1898×0.40/4 = 190g; Carbs = 1898×0.40/4 = 190g; Fat = 1898×0.20/9 = 42g.
The Mifflin-St Jeor equation (1990) is the most widely validated formula for predicting resting metabolic rate. Studies comparing it to indirect calorimetry measurements show it predicts BMR within 10% for most people, making it more accurate than the older Harris-Benedict equation (1919).
Balanced (40/30/30) works well for general health and moderate activity. High protein (40/40/20) is ideal for resistance training and muscle building. Low carb (20/40/40) can help with blood sugar control and fat adaptation. Ketogenic (5/25/70) is used for specific therapeutic and weight loss goals but requires careful planning to meet micronutrient needs.
Yes. A 500 kcal/day deficit produces approximately 0.5 kg (1 lb) of fat loss per week, which is within the recommended rate of 0.5–1 kg/week for sustainable weight loss. Larger deficits can cause muscle loss, nutrient deficiencies, and metabolic adaptation.
Fat has a higher energy density because fatty acid chains are more reduced (more C-H bonds) than carbohydrate or protein molecules. The Atwater general factors (fat=9, carbs=4, protein=4) are used in standard nutritional calculations, though actual digestibility varies slightly by food source.
The RDA for protein is 0.8g/kg/day for sedentary adults. For muscle building and retention during a caloric deficit, research supports 1.6–2.2g/kg/day. Older adults (50+) benefit from 1.2–1.6g/kg/day to counteract sarcopenia. This calculator's macro splits provide at least 1.5g/kg for most users.
The Mifflin-St Jeor equation has a margin of error of ±10%. If you track your intake and weight doesn't change as expected, adjust your target by 100–200 kcal in the appropriate direction. Factors like hormonal conditions, medications, and very low body fat percentage can affect actual metabolic rate.
This calculator accounts for exercise through the activity factor. If you use the moderately active (1.55) factor, exercise calories are already included in your TDEE. Do not double-count by also eating back calories from wearables or gym machines, which tend to overestimate exercise expenditure.
Macros (protein, carbs, fat) are the starting point, but micronutrients, fiber, phytonutrients, and meal timing also matter. Aim for 25–38g of fiber daily, mostly from whole foods. Use the companion Micronutrient Calculator for vitamins and minerals.
Recalculate every 4–6 weeks or whenever your weight changes by more than 3–5 kg, your activity level changes, or your goal changes. As you lose weight, your BMR decreases, so adjusting macros periodically prevents plateaus.
Yes, as long as you maintain a caloric deficit, the specific macro split is secondary for weight loss (energy balance is primary). However, higher protein intake preserves more lean mass during a deficit, and lower carb diets can reduce appetite for some individuals, making adherence easier.
Roboculator Team
The Roboculator Team explains calculations, planning tools, and practical formulas in clear language for real-life situations.
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