{
  "slug": "macro-split",
  "title": "Macro Split Calculator",
  "category": "Macros & Intake",
  "category_slug": "macros-intake",
  "tier": 1,
  "summary": "Convert calorie percentages into daily protein, carb, and fat gram targets based on your TDEE.",
  "description": "This calculator converts user-defined calorie percentages into daily gram targets for protein, carbohydrates, and fat based on total daily energy expenditure (TDEE). It accepts TDEE in kilocalories, protein percentage, and carbohydrate percentage as inputs, automatically derives fat as the remainder, then applies Atwater general factors (4 kcal/g for protein and carbs, 9 kcal/g for fat) to output gram quantities for each macronutrient. The macro split is a planning tool commonly used to structure meal composition for physique, performance, or general health goals.",
  "page_url": "https://fitmetriclab.com/en/tools/macros-intake/macro-split/",
  "api_url": "https://fitmetriclab.com/api/tools/macro-split.json",
  "formula": {
    "id": "macro_split",
    "expression": "g_{macro} = \\frac{\\text{TDEE} \\times \\text{pct}_{macro}}{k_{macro}}, \\quad \\text{pct}_f = 1 - \\text{pct}_p - \\text{pct}_c",
    "variables": [
      {
        "symbol": "\\text{TDEE}",
        "description": "Total daily energy expenditure"
      },
      {
        "symbol": "\\text{pct}_p",
        "description": "Protein percentage"
      },
      {
        "symbol": "\\text{pct}_c",
        "description": "Carbohydrate percentage"
      }
    ]
  },
  "inputs": [
    {
      "id": "tdee",
      "label": "TDEE",
      "type": "number",
      "unit": "kcal",
      "default": 2500,
      "min": 1000,
      "max": 6000,
      "step": 10
    },
    {
      "id": "protein_pct",
      "label": "Protein %",
      "type": "number",
      "unit": "%",
      "default": 30,
      "min": 0,
      "max": 100,
      "step": 1
    },
    {
      "id": "carbs_pct",
      "label": "Carbs %",
      "type": "number",
      "unit": "%",
      "default": 40,
      "min": 0,
      "max": 100,
      "step": 1
    }
  ],
  "worked_example": {
    "inputs": {
      "tdee": 2500,
      "protein_pct": 30,
      "carbs_pct": 40
    },
    "expected_output": "188 P / 250 C / 83 F (g)"
  },
  "result_summary_template": "With a TDEE of {tdee} kcal and macronutrient splits of {protein_pct}% protein and {carbs_pct}% carbs, the calculator converts those percentages into daily gram targets: {result}.",
  "methodology": "Multiplies user-defined protein and carbohydrate percentages by TDEE, calculates fat as the remainder (100 - protein% - carbs%), then divides protein and carb calories by 4 kcal/g and fat calories by 9 kcal/g using Atwater general factors (Merrill & Watt, 1955).",
  "sources": [
    {
      "label": "Merrill AL, Watt BK. Energy Value of Foods: Basis and Derivation. USDA Agriculture Handbook No. 74. 1955.",
      "url": "https://www.ars.usda.gov/ARSUserFiles/80400525/Data/Classics/ah74.pdf"
    },
    {
      "label": "Atwater WO, Benedict FG. Experiments on the Metabolism of Matter and Energy in the Human Body. USDA Office of Experiment Stations Bulletin 136. 1903.",
      "url": "https://www.nal.usda.gov/exhibits/speccoll/exhibits/show/agnic-early-nutrition/atwater"
    },
    {
      "label": "U.S. Food and Drug Administration. Guidance for Industry: A Food Labeling Guide – Appendix F: Calculate the Percent Daily Value. 2013.",
      "url": "https://www.fda.gov/regulatory-information/search-fda-guidance-documents/guidance-industry-food-labeling-guide"
    }
  ],
  "faqs": [
    {
      "question": "Why does the fat percentage adjust automatically?",
      "answer": "The tool uses a two-slider design: you set protein and carbs percentages, and fat is calculated as the remainder (100 - protein% - carbs%). This ensures the three macronutrients always sum to 100% without requiring manual balancing."
    },
    {
      "question": "What are the 4 and 9 conversion factors?",
      "answer": "These are the Atwater general factors: protein and carbohydrate each provide approximately 4 kilocalories per gram, while fat provides approximately 9 kilocalories per gram. They are standard coefficients used in nutrition labeling worldwide."
    },
    {
      "question": "Can I enter a custom fat percentage?",
      "answer": "No. Fat percentage is always derived as 100 minus the sum of protein and carbs percentages. If you want a specific fat target, adjust the protein or carbs sliders until fat reaches the desired value."
    },
    {
      "question": "What happens if protein plus carbs exceeds 100%?",
      "answer": "The calculator returns an error message asking you to reduce one percentage to leave room for fat. Macronutrient percentages must sum to 100%, so the tool prevents invalid splits."
    },
    {
      "question": "Does this tool recommend a macro split for my goals?",
      "answer": "No. It performs arithmetic conversion only. The choice of protein, carb, and fat percentages is entirely user-controlled. The tool does not prescribe ratios for fat loss, muscle gain, performance, or any other outcome."
    }
  ],
  "related_tools": [
    {
      "slug": "protein-intake",
      "title": "Protein Intake Calculator",
      "api_url": "https://fitmetriclab.com/api/tools/protein-intake.json",
      "page_url": "https://fitmetriclab.com/en/tools/macros-intake/protein-intake/"
    },
    {
      "slug": "water-intake",
      "title": "Water Intake Calculator",
      "api_url": "https://fitmetriclab.com/api/tools/water-intake.json",
      "page_url": "https://fitmetriclab.com/en/tools/macros-intake/water-intake/"
    },
    {
      "slug": "alcohol-calories",
      "title": "Alcohol Calories Calculator",
      "api_url": "https://fitmetriclab.com/api/tools/alcohol-calories.json",
      "page_url": "https://fitmetriclab.com/en/tools/macros-intake/alcohol-calories/"
    }
  ],
  "last_updated": "2026-04-22",
  "price": {
    "value": 0,
    "currency": "USD"
  },
  "runs_in_browser": true,
  "disclaimer": "Educational estimate produced from a published formula. Not medical, nutritional, or training advice. Calculations are deterministic — apply the formula to the inputs to reproduce the result."
}