Macronutrient Calculator
Split a daily calorie target into grams of protein, carbs, and fat using the 4/4/9 calories-per-gram rule. Compare balanced, low-carb, high-protein.
Medical disclaimer: This calculator is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. Results are general estimates and may not reflect your individual circumstances. Always consult a qualified healthcare professional before making decisions about your health.
Macronutrient Calculator
Calculator
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Formula: Protein(g) = Calories x Protein% / 4 | Fat(g) = Calories x Fat% / 9 | Carbs(g) = Calories x Carb% / 4
Worked example — 150g protein, 56g fat, 225g carbs
Formula
Protein(g) = Calories x Protein% / 4 | Fat(g) = Calories x Fat% / 9 | Carbs(g) = Calories x Carb% / 4
Each macronutrient has a caloric density: protein = 4 cal/g, carbohydrates = 4 cal/g, fat = 9 cal/g. Percentages should total 100%. Common splits: balanced (30/25/45), low-carb (35/40/25), keto (20/70/10).
Worked Examples
Example 1: 2000 cal, 30/25/45 split
Problem:2000 calories, 30% protein, 25% fat, 45% carbs
Solution:Protein: 150g (600 cal), Fat: 56g (504 cal), Carbs: 225g (900 cal)
Result:150g protein, 56g fat, 225g carbs
Frequently Asked Questions
What macro split should I use?
Balanced: 30% protein, 25% fat, 45% carbs. Low-carb: 35% protein, 40% fat, 25% carbs. Keto: 20% protein, 70% fat, 10% carbs. High-protein: 40% protein, 25% fat, 35% carbs.
How many grams of protein per meal?
Research suggests 30-50g of protein per meal optimizes muscle protein synthesis. Spread protein across 3-5 meals for best results.
How much protein do I need per day to build muscle?
Current evidence recommends 1.6–2.2g of protein per kilogram of body weight per day for muscle growth. For a 75kg person, that is 120–165g of protein daily. Spreading intake across 3–5 meals and consuming protein within 2 hours post-workout maximizes muscle protein synthesis. Exceeding 2.2g/kg provides minimal additional benefit for most people.
Are all dietary fats the same?
No. Unsaturated fats (avocado, olive oil, nuts, fish) support heart health and reduce inflammation. Saturated fats (butter, red meat, coconut oil) should be limited to under 10% of total calories. Trans fats (partially hydrogenated oils) are harmful and should be avoided. Your fat macro should prioritize unsaturated sources while limiting saturated fat intake.
Why does fat supply 9 calories per gram while protein and carbohydrate supply 4?
These are the Atwater factors, and they reflect chemistry. Fatty acids are long, highly reduced hydrocarbon chains with little oxygen, so oxidising them releases far more energy per gram than carbohydrate, whose carbons are already partly oxidised. Protein lands at 4 as well, after subtracting the energy lost in urea when nitrogen is excreted. This is why a modest change in the fat percentage moves your gram target much less than the same change on carbohydrate.
Why does the calculator refuse a protein and fat percentage that adds to 100 or more?
Carbohydrate is treated as the remainder rather than as its own input, so the three shares always close at exactly 100%. If protein plus fat reaches 100% there is nothing left to assign, and any value above it would imply a negative carbohydrate target. Entering 30% protein and 25% fat leaves 45% carbohydrate automatically. To go very low carbohydrate, raise the fat share and watch the remainder shrink rather than trying to set carbs directly.
How do I turn a macro percentage into grams per kilogram of body weight?
Take the calorie total, multiply by the percentage, divide by the macro's calorie density, then divide by your body mass in kilograms. On 2,000 calories with a 30% protein share: 2,000 x 0.30 = 600 calories, divided by 4 gives 150 g, and for a 75 kg person that is 2.0 g per kg. This conversion matters because protein guidance is usually published per kilogram, while the calculator works in percentages of intake.
What is the difference between total carbohydrate and net carbs?
Total carbohydrate on a label includes starches, sugars, fibre and sugar alcohols. Net carbs subtract fibre and part of the sugar alcohols on the reasoning that they are poorly digested and absorbed in the small intestine. The calculator works from total carbohydrate, because that is what the 4 calories per gram figure assumes. If you track net carbs instead, your logged intake will read lower than the target this tool produces.
Why is there usually a floor under the fat share rather than only a ceiling?
Fat is the carrier for the fat-soluble vitamins A, D, E and K and the only dietary source of the essential fatty acids linoleic and alpha-linolenic acid, which the body cannot synthesise. Pushing the fat percentage very low can also affect satiety and hormone-related processes. That is why general guidance frames fat as a range of total calories rather than something to minimise, and why very low-fat splits are best set with professional input.
How should the per-meal split change if I train late in the day?
The calculator divides each macro evenly by your meal count, which is a reasonable default because protein distribution across the day supports muscle protein synthesis. In practice many people shift carbohydrate toward the meals immediately before and after training, where it refills muscle glycogen, and keep protein even across every meal. Total daily intake still dominates the outcome, so treat timing as a refinement rather than the main lever.
References
Reviewed for accuracy by Rahul Singh, Health & Wellness Specialist · Editorial policy
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