Formula
The exact temperature conversion is:
°F = °C × 9/5 + 32
Gas marks use a conventional cookbook table from mark 1 at 140°C through mark 9 at 240°C. The nearest mark is chosen by Celsius distance. An exact tie keeps the lower mark.
Assumptions
- The entered temperature is a conventional oven setting, not a fan or convection offset.
- Gas marks outside 140°C to 240°C still show the nearest listed mark.
- Fahrenheit is exact for the value you type. Display rounding is one decimal place.
Worked example
180°C converts to 356°F and is conventional gas mark 4.
Input definitions
- Temperature
- The oven setting you already have, in Celsius or Fahrenheit.
- Gas mark
- The closest mark on the conventional 1-to-9 table. It is not a measured oven reading.
Limitations
Ovens vary. A gas mark is a nearest published equivalent, not a calibration of your oven. Fan settings often need a lower number than a conventional recipe.
Questions
Is gas mark 4 always 180°C?
On the conventional table used here, yes. A fan oven may need a lower setting for the same recipe.
What if my temperature sits halfway between two marks?
The lower mark is kept when the Celsius distance is equal.