{
  "id": "pressure-altitude",
  "version": "145a3ef217aa",
  "status": "published",
  "name": "Pressure Altitude Calculator",
  "question": "What's the pressure altitude?",
  "summary": "Pressure altitude calculator for pilots: the pressure altitude from the field elevation and altimeter setting, or from the station pressure, with the 1,000 ft per inch rule of thumb and the station pressure.",
  "category": "physics",
  "subcategory": "weather",
  "url": "https://www.acalculator.org/physics/pressure-altitude-calculator",
  "markdown": "https://www.acalculator.org/physics/pressure-altitude-calculator.md",
  "kind": "function",
  "method": "h(p) = 145,366.45 × (1 − (p ÷ 1,013.25)^0.190284) ft, p in hPa. From a station pressure: PA = h(p). From an altimeter setting A: PA = elevation + h(A); station pressure = 1,013.25 × (1 − PA ÷ 145,366.45)^(1 ÷ 0.190284). Rule of thumb: elevation + 1,000 × (29.92 − A in inHg).",
  "assumptions": [
    "The standard atmosphere: 1,013.25 hPa (29.92 inHg) and 15 °C at sea level, cooling 1.9812 °C per 1,000 ft.",
    "1 inHg = 33.8639 hPa (mercury at 0 °C under standard gravity)."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "from": {
        "title": "From",
        "description": "Work from the field elevation and altimeter setting, or from a station pressure.",
        "type": "string",
        "enum": [
          "altimeter",
          "station"
        ]
      },
      "elev": {
        "title": "Field elevation",
        "description": "The elevation of the airport or place, above mean sea level.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "minimum": -457.20000000000005,
        "maximum": 9144
      },
      "alt": {
        "title": "Altimeter setting",
        "description": "The altimeter setting (QNH) from ATIS, METAR or the tower, such as 29.92 inHg or 1013 hPa.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "pressure",
        "minimum": 80000,
        "maximum": 110000
      },
      "stn": {
        "title": "Station pressure",
        "description": "The actual air pressure at the station, not reduced to sea level.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "pressure",
        "minimum": 10000,
        "maximum": 110000
      }
    }
  },
  "outputs": {
    "pa": {
      "label": "Pressure altitude",
      "description": "The height in the standard atmosphere with this pressure.",
      "format": "quantity",
      "unit": "ft"
    },
    "rule": {
      "label": "Rule of thumb",
      "description": "Elevation + 1,000 ft × (29.92 − altimeter setting in inHg).",
      "format": "quantity",
      "unit": "ft"
    },
    "correction": {
      "label": "Altimeter correction",
      "description": "Pressure altitude − field elevation: h(altimeter setting).",
      "format": "quantity",
      "unit": "ft"
    },
    "stationHpa": {
      "label": "Station pressure (hPa)",
      "description": "The pressure at the station in hectopascals (millibars).",
      "format": "number"
    },
    "stationInHg": {
      "label": "Station pressure (inHg)",
      "description": "The pressure at the station in inches of mercury.",
      "format": "number"
    },
    "isa": {
      "label": "ISA temperature (°C)",
      "description": "The standard-atmosphere temperature at this pressure altitude: 15 − 1.9812 per 1,000 ft.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "from": "altimeter",
      "elev": "5000 ft",
      "alt": "29.72 inHg",
      "stn": "843 hPa"
    },
    "outputs": {
      "pa": 1580.8637351831057,
      "rule": 1584.96,
      "correction": 56.86373518310572,
      "stationHpa": 837.1358983473109,
      "stationInHg": 24.72060909887217,
      "isa": 4.7243857213098135
    },
    "text": "The pressure altitude is 5,187 ft."
  },
  "examples": [
    {
      "given": {
        "from": "station",
        "stn": 101325
      },
      "expect": {
        "pa": 0,
        "isa": 15
      },
      "source": "Wikipedia, Pressure altitude (h = 145,366.45 × [1 − (station pressure in mb ÷ 1,013.25)^0.190284] ft; rule of thumb PA = elevation + 1,000 × (29.92 − altimeter setting)), https://en.wikipedia.org/wiki/Pressure_altitude (retrieved 2026-10-05); hand calculation in content.mdx: 145,366.45 × (1 − 1^0.190284) = 0 ft",
      "tolerance": 1e-12
    },
    {
      "given": {
        "from": "station",
        "stn": 84300
      },
      "expect": {
        "pa": 1524.072639126988
      },
      "source": "Wikipedia, Pressure altitude (h = 145,366.45 × [1 − (station pressure in mb ÷ 1,013.25)^0.190284] ft; rule of thumb PA = elevation + 1,000 × (29.92 − altimeter setting)), https://en.wikipedia.org/wiki/Pressure_altitude (retrieved 2026-10-05); hand calculation in content.mdx: 145,366.45 × (1 − (843 ÷ 1,013.25)^0.190284) = 5,000.2 ft",
      "tolerance": 1e-12
    },
    {
      "given": {
        "from": "altimeter",
        "elev": 1524,
        "alt": 100643.47039093453
      },
      "expect": {
        "pa": 1580.8637351831057,
        "rule": 1584.96
      },
      "source": "Wikipedia, Pressure altitude (h = 145,366.45 × [1 − (station pressure in mb ÷ 1,013.25)^0.190284] ft; rule of thumb PA = elevation + 1,000 × (29.92 − altimeter setting)), https://en.wikipedia.org/wiki/Pressure_altitude (retrieved 2026-10-05); hand calculation in content.mdx: 29.72 inHg = 1,006.43 hPa; h = 186.56 ft; PA = 5,186.56 ft; rule of thumb 5,000 + 1,000 × 0.20 = 5,200 ft",
      "tolerance": 1e-9
    }
  ],
  "sources": [
    "Wikipedia, Pressure altitude: the NWS formula h = 145,366.45 × [1 − (p ÷ 1,013.25)^0.190284] ft and the rule PA = elevation + 1,000 × (29.92 − altimeter setting), retrieved 2026-10-05. https://en.wikipedia.org/wiki/Pressure_altitude",
    "National Weather Service, Pressure Altitude Calculator, retrieved 2026-10-05. https://www.weather.gov/epz/wxcalc_pressurealtitude",
    "NIST Special Publication 811 (2008), Appendix B.8: 1 ft = 0.3048 m; 1 inHg (0 °C) = 3,386.389 Pa, retrieved 2026-10-05. https://www.nist.gov/pml/special-publication-811"
  ],
  "related": [
    "density-altitude",
    "e6b",
    "crosswind"
  ],
  "changelog": []
}