Oven Temperature Converter

Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer Last updated: August 19, 2026

Gas Mark 4 Is Not a Temperature. It's a Dial Position.

Celsius and Fahrenheit are scales with formulas. The British gas mark is neither — it's a numbered setting on a gas oven dial, and its relationship to actual temperature is a published lookup table rather than an equation. Above gas mark 1 the steps are regular, 25°F per mark. Below it they aren't: the scale drops to quarter-marks to reach the low temperatures used for meringues and slow cooking. That irregularity is why a single multiply-and-add formula can't convert gas marks, and why this calculator interpolates across the reference table instead.

How the Conversion Works

Celsius and Fahrenheit convert between each other with the exact standard formulas:

Gas marks are handled differently. The calculator holds the standard gas-mark reference points, converts everything to Fahrenheit as a pivot, and uses piecewise-linear interpolation between the nearest two anchors when the input or output is a gas mark. Values beyond the ends of the table are extrapolated along the slope of the last segment.

The Reference Table the Calculator Uses

These are the exact anchor points built into the converter — the standard published UK oven table — with the Celsius column computed from each Fahrenheit anchor:

The table also carries a gas mark 0 anchor at 200°F (93.33°C) for the very low end. From gas mark 1 upward, every step is exactly 25°F.

Working From a Celsius Recipe

Recipes written in Celsius rarely land on a whole gas mark — the calculator returns the interpolated value, which is what the dial position should actually be:

Why It Matters in the Kitchen

• British recipes on a non-gas oven — a recipe specifying gas mark 6 needs 400°F or 204°C on an electric dial.
• American recipes on a UK gas oven — a 350°F cake is gas mark 4, exactly.
• Precision baking — pastry, choux and bread are unforgiving about oven temperature; a 25°F error is a whole gas mark and visible in the result.
• Older cookbooks — many pre-metric British books give gas marks only, with no Celsius equivalent printed at all.

One thing this converter deliberately doesn't do: adjust for fan or convection ovens. The usual guidance is to reduce a conventional temperature by about 20°C for a fan oven, but that's a manufacturer-specific rule of thumb, not a unit conversion — apply it after converting, and check your oven's manual.

How to Use This Calculator

1. Enter the temperature or gas mark number in the Value field. Fractional gas marks like 0.25 and 0.5 are accepted.
2. Choose what that number is in the first dropdown: Celsius, Fahrenheit or Gas Mark.
3. Choose what you want in the second dropdown.
4. Press Calculate. Negative gas marks are rejected, as is anything below absolute zero.

Related Calculations

For temperature outside the kitchen — including Kelvin and Rankine — see the Temperature Converter. Scaling a recipe's quantities as well? The Volume Converter handles cups, millilitres and fluid ounces.