{
  "entity_type": "unit_conversion_page",
  "id": "km-to-au",
  "name": "Kilometers to Astronomical units",
  "title": "Kilometers to Astronomical units Converter (km to au)",
  "description": "Convert kilometers to astronomical units: 1 km = 6.68459e-9 au. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.",
  "quantity": "length",
  "quantity_name": "Length",
  "base_unit": "m",
  "from_unit": {
    "symbol": "km",
    "display": "km",
    "name": "kilometers",
    "singular": "kilometer"
  },
  "to_unit": {
    "symbol": "au",
    "display": "au",
    "name": "astronomical units",
    "singular": "astronomical unit"
  },
  "linear": true,
  "factor": 6.684587122e-9,
  "inverse_factor": 149597870.7,
  "formula": "astronomical units = kilometers × 6.684587122e-9",
  "reverse_formula": "kilometers = astronomical units × 149597870.7",
  "unit_relation": "1 km = 6.68459e-9 au",
  "examples": [
    {
      "value": 5,
      "result": 3.34229e-8,
      "text": "5 km = 3.34229e-8 au"
    },
    {
      "value": 12.5,
      "result": 8.35573e-8,
      "text": "12.5 km = 8.35573e-8 au"
    },
    {
      "value": 100,
      "result": 6.68459e-7,
      "text": "100 km = 6.68459e-7 au"
    }
  ],
  "table": [
    {
      "km": 1,
      "au": 6.68459e-9
    },
    {
      "km": 2,
      "au": 1.33692e-8
    },
    {
      "km": 3,
      "au": 2.00538e-8
    },
    {
      "km": 4,
      "au": 2.67383e-8
    },
    {
      "km": 5,
      "au": 3.34229e-8
    },
    {
      "km": 6,
      "au": 4.01075e-8
    },
    {
      "km": 7,
      "au": 4.67921e-8
    },
    {
      "km": 8,
      "au": 5.34767e-8
    },
    {
      "km": 9,
      "au": 6.01613e-8
    },
    {
      "km": 10,
      "au": 6.68459e-8
    },
    {
      "km": 15,
      "au": 1.00269e-7
    },
    {
      "km": 20,
      "au": 1.33692e-7
    },
    {
      "km": 25,
      "au": 1.67115e-7
    },
    {
      "km": 30,
      "au": 2.00538e-7
    },
    {
      "km": 40,
      "au": 2.67383e-7
    },
    {
      "km": 50,
      "au": 3.34229e-7
    },
    {
      "km": 75,
      "au": 5.01344e-7
    },
    {
      "km": 100,
      "au": 6.68459e-7
    },
    {
      "km": 200,
      "au": 0.00000133692
    },
    {
      "km": 250,
      "au": 0.00000167115
    },
    {
      "km": 500,
      "au": 0.00000334229
    },
    {
      "km": 1000,
      "au": 0.00000668459
    }
  ],
  "faq": [
    {
      "q": "How many astronomical units are in one kilometer?",
      "a": "1 km = 6.68459e-9 au. The factor comes from the SI definitions of both units (NIST SP 811 / BIPM), so it is exact or correct to at least 10 significant figures."
    },
    {
      "q": "What is the formula to convert kilometers to astronomical units?",
      "a": "Multiply the value in kilometers by 6.684587122e-9: astronomical units = kilometers × 6.684587122e-9. For example, 5 km = 3.34229e-8 au."
    },
    {
      "q": "How do I convert astronomical units back to kilometers?",
      "a": "Multiply by the inverse factor 149597870.7 (kilometers = astronomical units × 149597870.7), or use the astronomical units-to-kilometers page."
    }
  ],
  "sources": [
    {
      "name": "NIST Special Publication 811 – Guide for the Use of the International System of Units (SI), Appendix B conversion factors",
      "url": "https://www.nist.gov/pml/special-publication-811",
      "type": "standard",
      "retrieved_at": "2026-09-24"
    },
    {
      "name": "BIPM – The International System of Units (SI Brochure, 9th edition)",
      "url": "https://www.bipm.org/en/publications/si-brochure",
      "type": "standard",
      "retrieved_at": "2026-09-24"
    },
    {
      "name": "Wikipedia – Conversion of units",
      "url": "https://en.wikipedia.org/wiki/Conversion_of_units",
      "type": "reference",
      "retrieved_at": "2026-09-24"
    }
  ],
  "freshness": {
    "type": "static",
    "max_age_seconds": null,
    "note": "Fixed conversion factors (NIST/BIPM definitions); results never go stale."
  },
  "api": {
    "convert": "https://tttkmbb.com/api/v1/convert?value=5&from_unit=km&to_unit=au",
    "calculator": "https://tttkmbb.com/api/v1/calculate/length?value=5&from_unit=km&to_unit=au",
    "mcp_tool": "convert_units",
    "mcp_arguments": {
      "value": 5,
      "from_unit": "km",
      "to_unit": "au"
    }
  },
  "links": {
    "html": "https://tttkmbb.com/conversion/km-to-au",
    "markdown": "https://tttkmbb.com/conversion/km-to-au.md",
    "json": "https://tttkmbb.com/conversion/km-to-au.json",
    "reverse": "https://tttkmbb.com/conversion/au-to-km",
    "quantity_converter": "https://tttkmbb.com/conversion/length",
    "units": "https://tttkmbb.com/api/v1/units?quantity=length"
  },
  "timestamp": "2026-09-24"
}