{
  "schemaVersion": 1,
  "version": "units-2026-10-24",
  "status": "research-verified unit definitions; food-specific mass conversions require separate audited anchors",
  "basis": {
    "inchCentimeters": "2.54",
    "usGallonCubicInches": "231",
    "usGallonFluidOunces": "128",
    "usCupFluidOunces": "8",
    "usTablespoonFluidOunces": "0.5",
    "usTablespoonTeaspoons": "3",
    "avoirdupoisPoundGrams": "453.59237",
    "avoirdupoisPoundOunces": "16"
  },
  "source": {
    "id": "nist-hb44-2024-units",
    "url": "https://www.nist.gov/system/files/documents/2024/01/14/NIST%20HB%2044%202024%20Appendix%20C%20General%20Tables%20of%20Units%20of%20Measurement.pdf",
    "sha256": "244294a5c8b344ab439111c43fb753ab825f6521eaf34147b0fb1339fa8e5ff3",
    "locators": [
      "Appendix C, units of length, mass and capacity tables",
      "Appendix C, tables of equivalents: exact definitions distinguished from rounded household equivalents"
    ]
  },
  "units": {
    "g": {
      "dimension": "mass",
      "grams": "1"
    },
    "kg": {
      "dimension": "mass",
      "grams": "1000"
    },
    "oz": {
      "dimension": "mass",
      "grams": "28.349523125"
    },
    "lb": {
      "dimension": "mass",
      "grams": "453.59237"
    },
    "ml": {
      "dimension": "volume",
      "milliliters": "1"
    },
    "l": {
      "dimension": "volume",
      "milliliters": "1000"
    },
    "us-tsp": {
      "dimension": "volume",
      "milliliters": "4.92892159375"
    },
    "us-tbsp": {
      "dimension": "volume",
      "milliliters": "14.78676478125"
    },
    "us-cup": {
      "dimension": "volume",
      "milliliters": "236.5882365"
    },
    "us-fl-oz": {
      "dimension": "volume",
      "milliliters": "29.5735295625"
    },
    "metric-tsp-5ml": {
      "dimension": "volume",
      "milliliters": "5"
    },
    "metric-tbsp-15ml": {
      "dimension": "volume",
      "milliliters": "15"
    }
  },
  "policies": [
    "These constants convert units of the same dimension; volume to mass needs a food/preparation-specific source or user measurement.",
    "Unqualified tbsp/tsp in U.S. input mean U.S. customary units. Metric spoons are explicit 15 mL/5 mL options; do not silently reinterpret old entries.",
    "Each reviewed food uses one coherent volume-to-mass anchor per data version. Other source portions remain evidence; differences from rounded portions must be disclosed.",
    "Store canonical grams, original input and conversion provenance; display-unit changes never recalculate or overwrite canonical grams.",
    "A recipe’s ingredient volumes do not establish its final blended volume. Use weighed total or a measured finished volume."
  ]
}