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Oven Temperature Converter

Converts an oven setting between degrees Celsius, degrees Fahrenheit and British gas marks, reports the descriptive term (slow, moderate, hot) and the equivalent fan (convection) oven setting, which is 20 °C lower.

When to use

A recipe gives an oven temperature in a scale your oven does not use, mentions a gas mark, or you need the fan-oven equivalent of a conventional temperature.

Do not use when: You need a general temperature conversion that is not an oven setting (use temperature), or internal food doneness temperatures (use turkey-cooking-time for poultry).

Formula

°F = °C × 9/5 + 32; gas mark n ≥ 1: °F = 250 + 25·n (gas mark 1 = 275 °F, +25 °F per mark); gas mark ½ = 250 °F, ¼ = 225 °F; fan °C = conventional °C − 20; fan °F = conventional °F − 25

Gas mark values follow the British scale defined in 25 °F steps from 275 °F. The 20 °C (25 °F) fan-oven reduction is the usual manufacturer guidance; recipes often round Celsius values (e.g. gas mark 6 = 400 °F = 204 °C is printed as 200 °C).

Inputs

Parameter	Type	Required	Description
`temperature`	number	yes	Oven temperature in temperature_unit, or the gas mark number (0.25, 0.5, 1 … 10). Range: ≥ 0, ≤ 600
`temperature_unit`	enum: c \| f \| gas_mark	default c	Scale of the input value.
`input_is_fan_oven`	boolean	default false	true if the given temperature is already a fan/convection setting; it is then raised by 20 °C to the conventional equivalent before conversion.

Outputs

Output	Type	Unit	Description
`celsius`	number	°C	Conventional (static) oven temperature in Celsius.
`fahrenheit`	number	°F	Conventional oven temperature in Fahrenheit.
`gas_mark`	string		Nearest British gas mark (¼, ½, 1–10).
`gas_mark_exact`	number		Unrounded gas mark position, (°F − 250) / 25 for gas mark 1 and above.
`fan_oven_c`	number	°C	Conventional temperature minus 20 °C.
`fan_oven_f`	number	°F	Conventional Fahrenheit temperature minus 25 °F (US convection rule).
`description`	string		Traditional term for this heat: very slow, slow, moderately slow, moderate, moderately hot, hot, very hot.
`conversion_table`	list		Gas marks ¼–10 with °F, °C and fan °C.

Example

180 °C: {"temperature":180,"temperature_unit":"c"} → {"celsius":180,"fahrenheit":356,"gas_mark":"4","gas_mark_exact":4.24,"fan_oven_c":160,"fan_oven_f":331,"description":"Moderate"}

Gas mark 6: {"temperature":6,"temperature_unit":"gas_mark"} → {"fahrenheit":400,"celsius":204,"gas_mark":"6","fan_oven_c":184,"description":"Moderately hot"}

GET https://tttkmbb.com/api/v1/calculate/oven-temperature?temperature=180&temperature_unit=c

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/oven-temperature (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/oven-temperature · Markdown: https://tttkmbb.com/food/oven-temperature.md · JSON definition: https://tttkmbb.com/food/oven-temperature.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="oven-temperature"
OpenAPI operationId: convert_oven_temperature
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

Wikipedia – Gas mark (reference)
Wikipedia – Oven temperatures (descriptive terms and fan-oven adjustment) (reference)

FAQ

Why does my recipe say gas mark 4 = 180 °C when the table gives 177 °C?

Gas mark 4 is defined as 350 °F = 176.7 °C; recipe writers round to the nearest 10 °C. Ovens are rarely accurate to better than ±10 °C anyway.

Should I always reduce the temperature for a fan oven?

Yes, by about 20 °C (25 °F) unless the recipe already states a fan setting; the moving air transfers heat faster. Some recipes also shorten the time by roughly 10 %.

How do I enter gas mark ½ or ¼?

As 0.5 or 0.25 with temperature_unit=gas_mark.

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