{
  "id": "oven-conversions",
  "title": "Oven temperature conversions — UK gas mark, conventional, fan-assisted, Fahrenheit",
  "description": "Gas mark ↔ conventional °C/°F ↔ fan-assisted °C/°F, with the published fan reduction convention stated separately from the measured values.",
  "version": "1.0.0",
  "updated": "2026-08-27",
  "license": "CC-BY-4.0",
  "attribution": "ctofconverter.com",
  "languages": [
    "en"
  ],
  "page": "/fan-oven-conversion-chart",
  "provenance": [
    {
      "source": "Wikipedia — Gas mark, 'Conversion table' (its own references: BBC Good Food 'Conversion Guides'; The Guardian, 'Cooking conversion charts', 24 Nov 2007)",
      "url": "https://en.wikipedia.org/wiki/Gas_mark",
      "checkedOn": "2026-08-27",
      "note": "Secondary source, used because it reproduces the two published conversion guides in one table. Conventional-oven values in this dataset are taken verbatim from that table (110/120/140/150/170/180/190/200/220/230/240/260 °C at 25 °F steps)."
    },
    {
      "source": "ctofconverter.com — Fan oven conversion chart",
      "url": "https://ctofconverter.com/fan-oven-conversion-chart",
      "checkedOn": "2026-08-27",
      "note": "The site's own gas-mark rows were corrected to match the table above on 2026-08-27. The previous revision labelled conventional values as fan values and had Gas Mark 3, 5 and 7 wrong; do not copy the pre-2026-08-27 revision."
    }
  ],
  "columns": [
    {
      "key": "gas_mark",
      "label": "UK Gas Mark",
      "type": "string"
    },
    {
      "key": "conventional_c",
      "label": "Conventional oven",
      "unit": "°C",
      "type": "number"
    },
    {
      "key": "conventional_f",
      "label": "Conventional oven",
      "unit": "°F",
      "type": "number"
    },
    {
      "key": "fan_c",
      "label": "Fan / convection oven",
      "unit": "°C",
      "type": "number"
    },
    {
      "key": "fan_f",
      "label": "Fan / convection oven",
      "unit": "°F",
      "type": "number"
    },
    {
      "key": "descriptor",
      "label": "Heat level",
      "type": "string"
    },
    {
      "key": "typical_uses",
      "label": "Typical uses",
      "type": "string"
    }
  ],
  "rows": [
    {
      "gas_mark": "1/4",
      "conventional_c": 110,
      "conventional_f": 225,
      "fan_c": 90,
      "fan_f": 194,
      "descriptor": "Very slow / very low",
      "typical_uses": ""
    },
    {
      "gas_mark": "1/2",
      "conventional_c": 120,
      "conventional_f": 250,
      "fan_c": 100,
      "fan_f": 212,
      "descriptor": "Very slow / very low",
      "typical_uses": ""
    },
    {
      "gas_mark": "1",
      "conventional_c": 140,
      "conventional_f": 275,
      "fan_c": 120,
      "fan_f": 248,
      "descriptor": "Slow / low",
      "typical_uses": "Meringues, delicate baking"
    },
    {
      "gas_mark": "2",
      "conventional_c": 150,
      "conventional_f": 300,
      "fan_c": 130,
      "fan_f": 266,
      "descriptor": "Slow / low",
      "typical_uses": "Slow cooking, casseroles"
    },
    {
      "gas_mark": "3",
      "conventional_c": 170,
      "conventional_f": 325,
      "fan_c": 150,
      "fan_f": 302,
      "descriptor": "Moderately slow / warm",
      "typical_uses": "Fruit cakes, casseroles"
    },
    {
      "gas_mark": "4",
      "conventional_c": 180,
      "conventional_f": 350,
      "fan_c": 160,
      "fan_f": 320,
      "descriptor": "Moderate / medium",
      "typical_uses": "Sponge cakes, muffins, cookies, everyday baking"
    },
    {
      "gas_mark": "5",
      "conventional_c": 190,
      "conventional_f": 375,
      "fan_c": 170,
      "fan_f": 338,
      "descriptor": "Moderate / moderately hot",
      "typical_uses": "Fruit pies, casseroles, fish, scones"
    },
    {
      "gas_mark": "6",
      "conventional_c": 200,
      "conventional_f": 400,
      "fan_c": 180,
      "fan_f": 356,
      "descriptor": "Moderately hot",
      "typical_uses": "Roasting meats and vegetables, baking bread"
    },
    {
      "gas_mark": "7",
      "conventional_c": 220,
      "conventional_f": 425,
      "fan_c": 200,
      "fan_f": 392,
      "descriptor": "Hot",
      "typical_uses": "Roasting meats, puff pastry"
    },
    {
      "gas_mark": "8",
      "conventional_c": 230,
      "conventional_f": 450,
      "fan_c": 210,
      "fan_f": 410,
      "descriptor": "Hot / very hot",
      "typical_uses": ""
    },
    {
      "gas_mark": "9",
      "conventional_c": 240,
      "conventional_f": 475,
      "fan_c": 220,
      "fan_f": 428,
      "descriptor": "Very hot",
      "typical_uses": "Pizza, artisan bread, searing"
    },
    {
      "gas_mark": "10",
      "conventional_c": 260,
      "conventional_f": 500,
      "fan_c": 240,
      "fan_f": 464,
      "descriptor": "Extremely hot (less common marking)",
      "typical_uses": ""
    }
  ],
  "notes": [
    "conventional_c / conventional_f are the published table values. fan_c / fan_f are derived, not published: they apply the common UK convention 'set a fan/convection oven 20 °C lower than a conventional oven' and then convert exactly (°F = °C × 9/5 + 32).",
    "The fan reduction is a convention, not a physical constant. Published advice ranges from 15 °C to 20 °C (some manufacturers say up to 25 °C); oven fans differ. Use an oven thermometer for anything temperature-sensitive.",
    "Gas marks are a gas-oven dial scale. Most fan-assisted ovens are electric and are set in degrees, so a 'gas mark in a fan oven' is always a derived figure, never a dial reading.",
    "Celsius values in published tables are rounded to the nearest 10 °C; exact conversions of the Fahrenheit column will therefore differ by a few degrees. The Fahrenheit column is the finer-grained one."
  ]
}