{
  "id": "kmh-to-mph",
  "version": "484b836ca17b",
  "status": "published",
  "name": "Km/h to Mph Converter",
  "question": "How do I convert km/h to mph?",
  "summary": "Converts kilometers per hour (km/h) to miles per hour (mph) and back, with the exact unit definitions.",
  "category": "convert",
  "subcategory": "units",
  "url": "https://www.acalculator.org/convert/kmh-to-mph",
  "markdown": "https://www.acalculator.org/convert/kmh-to-mph.md",
  "kind": "formulas",
  "method": "mph = km/h × 0.621371192237 (the same as km/h ÷ 1.609344)",
  "assumptions": [
    "1 kilometer per hour = 0.621371192237 miles per hour, from the exact definitions in NIST SP 811.",
    "Exact on the typed decimals: at most 6 decimal places (6 significant digits below 0.0001), rounded half up; an answer of 1 billion or more shows at most 15 significant digits."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "value": {
        "title": "Kilometers per hour (km/h)",
        "description": "The amount in kilometers per hour to convert.",
        "type": "number",
        "minimum": 0,
        "maximum": 1000000000000
      },
      "result": {
        "title": "Miles per hour (mph)",
        "description": "The same amount in miles per hour.",
        "type": "number",
        "minimum": 0,
        "maximum": 621371192237.334
      }
    }
  },
  "solve": {
    "fillAny": 1,
    "variables": [
      "value",
      "result"
    ],
    "inputsOnly": []
  },
  "outputs": {
    "value": {
      "label": "Kilometers per hour (km/h)",
      "description": "The amount in kilometers per hour to convert.",
      "format": "number"
    },
    "result": {
      "label": "Miles per hour (mph)",
      "description": "The amount in miles per hour.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "value": 1
    },
    "outputs": {
      "result": 0.621371192237334
    },
    "text": "1 km/h = 0.621371 mph."
  },
  "examples": [
    {
      "given": {
        "value": 1
      },
      "expect": {
        "result": 0.621371192237334
      },
      "source": "exact unit definitions in NIST SP 811 (2008), Appendix B.8"
    },
    {
      "given": {
        "value": 100
      },
      "expect": {
        "result": 62.1371192237334
      },
      "source": "exact unit definitions in NIST SP 811 (2008), Appendix B.8"
    },
    {
      "given": {
        "result": 62.1371192237334
      },
      "expect": {
        "value": 100
      },
      "source": "exact unit definitions in NIST SP 811 (2008), Appendix B.8"
    }
  ],
  "sources": [
    "NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B.8: Factors for Units Listed Alphabetically (bold factors are exact), retrieved 2026-10-18. https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8",
    "NIST, U.S. Survey Foot: Revised Unit Conversion Factors: 1 acre = 43,560 ft² = 4,046.856 422 4 m² and 1 mile = 5,280 ft = 1,609.344 m, exact with the international foot, retrieved 2026-10-18. https://www.nist.gov/pml/us-surveyfoot/revised-unit-conversion-factors"
  ],
  "related": [
    "mph-to-kmh"
  ],
  "changelog": []
}