{
  "id": "carb",
  "version": "774502710de9",
  "status": "published",
  "name": "Carb Calculator",
  "question": "How many carbs should I eat a day?",
  "summary": "Finds grams of carbohydrate a day from your daily calories and a carb share, with the 45% to 65% range the Dietary Guidelines give for adults, grams per meal, and the 130 g RDA.",
  "category": "health",
  "subcategory": "nutrition",
  "url": "https://www.acalculator.org/health/carb-calculator",
  "markdown": "https://www.acalculator.org/health/carb-calculator.md",
  "kind": "function",
  "method": "carbs (g) = calories × share ÷ 100 ÷ 4; at 45% and 65% for the AMDR range; per meal = carbs ÷ meals. The RDA is 130 g a day.",
  "assumptions": [
    "Carbohydrate gives 4 calories per gram (the general factor in US nutrition labels).",
    "The 45% to 65% range (AMDR) and the 130 g RDA are for healthy adults and children 1 year and older; pregnancy and breastfeeding have higher RDAs, and a doctor or dietitian may advise otherwise.",
    "The page does not estimate calories; type your own figure."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "cal": {
        "title": "Calories a day",
        "description": "The calories you eat, or plan to eat, each day.",
        "type": "number",
        "minimum": 500,
        "maximum": 10000
      },
      "pct": {
        "title": "Calories from carbs",
        "description": "The share of your calories that comes from carbohydrate; adults are advised 45% to 65%.",
        "type": "number",
        "x-unit": "percent",
        "minimum": 0,
        "maximum": 100
      },
      "meals": {
        "title": "Meals and snacks a day",
        "description": "How many times a day you eat, to split the carbs evenly.",
        "type": "integer",
        "minimum": 1,
        "maximum": 12
      }
    }
  },
  "outputs": {
    "carbs": {
      "label": "Carbs a day",
      "description": "Calories × share ÷ 100 ÷ 4 calories per gram.",
      "format": "quantity",
      "unit": "g"
    },
    "low": {
      "label": "At 45% of calories",
      "description": "The low end of the adult AMDR range.",
      "format": "quantity",
      "unit": "g"
    },
    "high": {
      "label": "At 65% of calories",
      "description": "The high end of the adult AMDR range.",
      "format": "quantity",
      "unit": "g"
    },
    "perMeal": {
      "label": "Carbs per meal",
      "description": "Carbs a day ÷ meals and snacks.",
      "format": "quantity",
      "unit": "g"
    },
    "kcal": {
      "label": "Calories from carbs",
      "description": "Calories × share ÷ 100.",
      "format": "number"
    },
    "range": {
      "label": "Compared with 45% to 65%",
      "description": "Whether the share is below, within, or above the adult AMDR range.",
      "format": "text"
    },
    "rda": {
      "label": "Compared with the 130 g RDA",
      "description": "Whether carbs a day reach the RDA of 130 g.",
      "format": "text"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "cal": 2000,
      "pct": 50,
      "meals": 3
    },
    "outputs": {
      "carbs": 0.25,
      "low": 0.225,
      "high": 0.325,
      "perMeal": 0.08333333333333333,
      "kcal": 1000,
      "range": "within the 45% to 65% range",
      "rda": "at or above 130 g"
    },
    "text": "Eat about 250 g of carbs a day (within the 45% to 65% range)."
  },
  "examples": [
    {
      "given": {
        "cal": 2000,
        "pct": 50,
        "meals": 3
      },
      "expect": {
        "carbs": 0.25,
        "low": 0.225,
        "high": 0.325,
        "perMeal": 0.08333333333333333,
        "kcal": 1000,
        "range": "within the 45% to 65% range"
      },
      "source": "Slavin J, Carlson J. Carbohydrates. Advances in Nutrition 2014;5(6):760-761 (IOM RDA for carbohydrate 130 g/d; AMDR 45–65% of total calories), https://pmc.ncbi.nlm.nih.gov/articles/PMC4224210/ (retrieved 2026-10-02); U.S. Department of Agriculture and U.S. Department of Health and Human Services, Dietary Guidelines for Americans, 2020-2025, Appendix 1 (carbohydrate: RDA 130 g a day; AMDR 45% to 65% of calories for adults), https://www.dietaryguidelines.gov/sites/default/files/2021-03/Dietary_Guidelines_for_Americans-2020-2025.pdf; 21 CFR 101.9(c)(1)(i)(C) (4 calories per gram of carbohydrate), https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-101/subpart-A/section-101.9; hand calculation in content.mdx: 2,000 × 0.50 ÷ 4 = 250 g; 2,000 × 0.45 ÷ 4 = 225 g; 2,000 × 0.65 ÷ 4 = 325 g"
    },
    {
      "given": {
        "cal": 1800,
        "pct": 20,
        "meals": 3
      },
      "expect": {
        "carbs": 0.09,
        "range": "below the 45% to 65% range (low carb)",
        "rda": "40 g below 130 g"
      },
      "source": "U.S. Department of Agriculture and U.S. Department of Health and Human Services, Dietary Guidelines for Americans, 2020-2025, Appendix 1 (carbohydrate: RDA 130 g a day; AMDR 45% to 65% of calories for adults), https://www.dietaryguidelines.gov/sites/default/files/2021-03/Dietary_Guidelines_for_Americans-2020-2025.pdf; 21 CFR 101.9(c)(1)(i)(C) (4 calories per gram of carbohydrate), https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-101/subpart-A/section-101.9; hand calculation in content.mdx: 1,800 × 0.20 ÷ 4 = 90 g, 130 − 90 = 40 g"
    },
    {
      "given": {
        "cal": 2600,
        "pct": 60,
        "meals": 4
      },
      "expect": {
        "carbs": 0.39,
        "perMeal": 0.0975,
        "high": 0.4225,
        "rda": "at or above 130 g"
      },
      "source": "U.S. Department of Agriculture and U.S. Department of Health and Human Services, Dietary Guidelines for Americans, 2020-2025, Appendix 1 (carbohydrate: RDA 130 g a day; AMDR 45% to 65% of calories for adults), https://www.dietaryguidelines.gov/sites/default/files/2021-03/Dietary_Guidelines_for_Americans-2020-2025.pdf; 21 CFR 101.9(c)(1)(i)(C) (4 calories per gram of carbohydrate), https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-101/subpart-A/section-101.9; hand calculation in content.mdx: 2,600 × 0.60 ÷ 4 = 390 g, ÷ 4 meals = 97.5 g"
    }
  ],
  "sources": [
    "U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025, Appendix 1 (carbohydrate: RDA 130 g a day; AMDR 45% to 65% of calories for adults). https://www.dietaryguidelines.gov/sites/default/files/2021-03/Dietary_Guidelines_for_Americans-2020-2025.pdf",
    "Slavin J, Carlson J. Carbohydrates. Advances in Nutrition. 2014;5(6):760-761 (the IOM RDA for carbohydrate is 130 g/d for adults and children aged 1 year and older; the AMDR is 45–65% of total calories). https://pmc.ncbi.nlm.nih.gov/articles/PMC4224210/ (retrieved 2026-10-02)",
    "Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press; 2005. https://www.nationalacademies.org/publications/10490",
    "U.S. Code of Federal Regulations, 21 CFR 101.9(c)(1)(i)(C): general factor of 4 calories per gram for total carbohydrate. https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-101/subpart-A/section-101.9"
  ],
  "related": [
    "macro",
    "protein",
    "calorie",
    "tdee"
  ],
  "changelog": []
}