Daily calories split into carbs, protein and fat — weight & height in any unit.
Protein (g) = (C × P%) ÷ 4 Carbs (g) = (C × K%) ÷ 4 Fat (g) = (C × F%) ÷ 9
Each macronutrient contributes a fixed number of calories per gram:
Given a total daily calorie target (C) and percentage targets for each macro (P%, K%, F% — where P% + K% + F% = 100%), the grams of each macro are calculated as follows:
Protein (g) = (2,200 × 0.35) ÷ 4 = 770 ÷ 4 = 192.5 g ≈ 193 g Carbs (g) = (2,200 × 0.40) ÷ 4 = 880 ÷ 4 = 220 g Fat (g) = (2,200 × 0.25) ÷ 9 = 550 ÷ 9 = 61.1 g ≈ 61 g Calorie check: (193 × 4) + (220 × 4) + (61 × 9) = 772 + 880 + 549 = 2,201 kcal ✓ (1 kcal rounding difference)
Result: Protein: ~193 g/day | Carbohydrates: 220 g/day | Fat: ~61 g/day
For a person eating 2,200 kcal per day on a 35/40/25 split, the daily macro targets work out to roughly 193 g of protein, 220 g of carbohydrates, and 61 g of fat. The tiny 1 kcal discrepancy from 2,200 is purely due to rounding grams to whole numbers — a negligible real-world difference. These figures give you concrete numbers to hit when logging meals, making flexible dieting (IIFYM) straightforward and practical.
Macronutrients (macros) are the three primary nutrient categories that provide energy:
| Macronutrient | Calories per gram | Primary role | |---|---|---| | Protein | 4 kcal/g | Muscle repair, enzymes, hormones | | Carbohydrates | 4 kcal/g | Primary fuel for brain and muscles | | Fat | 9 kcal/g | Hormone production, fat-soluble vitamins, energy reserve |
The total calories you eat determines weight gain or loss over time, but the distribution of those calories across macros affects body composition, energy levels, satiety, and athletic performance.
| Goal | Protein % | Carbs % | Fat % | |---|---|---|---| | General maintenance | 20–30% | 45–55% | 25–35% | | Fat loss (cutting) | 30–40% | 30–40% | 25–35% | | Muscle gain (bulking) | 25–35% | 40–50% | 20–30% | | Endurance performance | 15–25% | 50–60% | 20–30% | | Low-carb / keto | 25–35% | 5–10% | 60–75% |
These are starting points. Individual response, food preferences, and medical conditions should all inform your final targets.
IIFYM is a flexible dieting philosophy that emphasises hitting macro gram targets rather than following rigid meal plans. Research supports tracking protein intake in particular as a key lever for body composition — higher protein diets are consistently associated with greater satiety and preservation of lean mass during a caloric deficit.
For most people focused on body composition, protein is the macro to anchor first. The International Society of Sports Nutrition recommends 1.4–2.0 g of protein per kilogram of body weight per day for exercising individuals, with some evidence supporting up to 2.2 g/kg for those in significant caloric deficits.
The 4-4-9 calorie-per-gram values (the Atwater system) are averages. Real food digestion efficiency varies, but the Atwater factors remain the universal standard used on nutrition labels worldwide.
**Macronutrients** (protein, carbs, fat) are consumed in large quantities and provide energy measured in calories. **Micronutrients** (vitamins and minerals) are needed in tiny amounts and do not provide calories directly but are essential for biochemical functions. A complete diet must address both.
Either approach is used in practice. Calculating protein needs based on **goal (lean) body weight** is common for overweight individuals, as it avoids over-allocating protein relative to actual lean mass needs. For people close to their goal weight, current weight works fine. Your calorie target should always be set relative to your goal (deficit, surplus, or maintenance).
Use a **TDEE (Total Daily Energy Expenditure) calculator**, which estimates your calorie needs based on age, sex, height, weight, and activity level using equations like Mifflin-St Jeor. Once you have your TDEE, apply a deficit (typically 10–25% below TDEE for fat loss) or a surplus (5–15% above for muscle gain) and enter that adjusted figure here.
A **40% carbs / 40% protein / 20% fat** split is a popular choice for lean bulking. The high protein supports muscle protein synthesis; the high carbohydrate allocation fuels training intensity and glycogen replenishment. Fat at 20% still covers essential fatty acid and hormone needs. It is a reasonable evidence-backed starting point for muscle gain.
A common starting point for fat loss is **35% protein / 35% carbohydrates / 30% fat**. The elevated protein helps preserve muscle mass and increases satiety during a caloric deficit. Adjust carbs and fat based on food preference — both can work for fat loss as long as the calorie deficit is maintained.
For active individuals, the International Society of Sports Nutrition recommends **1.4–2.0 g of protein per kilogram of body weight per day** (roughly 0.64–0.91 g per pound). During aggressive cutting phases, some research supports going up to 2.2–2.4 g/kg to minimise muscle loss. Use this range as a reference when setting your protein percentage.
Yes. For a standard ketogenic diet, set fat to roughly **70–75%**, protein to **20–25%**, and carbohydrates to **5–10%**. The calculator will return the gram targets for those percentages. Note that on keto, most people target net carbs (total carbs minus fibre), so real carb-food choices matter beyond just the gram total.
Fat is a more energy-dense molecule. At the chemical level, fatty acids have a higher ratio of carbon-hydrogen bonds relative to oxygen compared to carbohydrates, releasing more energy (ATP) when oxidised. This is why 1 gram of fat yields 9 kcal while 1 gram of protein or carbohydrate yields only 4 kcal.
No. Exact daily precision is unnecessary for most people. Consistently hitting your targets within ±10 g over the course of a week produces the same physiological result. Focus on weekly averages rather than daily perfection to avoid stress and decision fatigue.
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