The common recipe line 200 °C / 400 °F / Gas Mark 6 / about 180 °C fan is easier than the 180-degree example because its Celsius and Gas Mark values align exactly with the fixed table. It is still not an exact Celsius–Fahrenheit identity: 200 °C converts to 392 °F, while 400 °F converts to about 204.4 °C. The grouped 400 setting is a practical round number. Fan 180 remains a broad minus-20 guide, not a guaranteed result.
Exact conversion: 200 °C is 392 °F
Using F = C × 9/5 + 32 gives 200 × 9/5 = 360, then 360 + 32 = 392 °F. The common recipe value 400 °F is eight degrees Fahrenheit higher. That small difference may be acceptable in a rounded cross-unit chart, but it should remain visible as rounding. If a technical process requires 200 °C precisely, choose 392 °F rather than silently replacing it with recipe shorthand.
Gas Mark 6 is exactly the 200 °C / 400 °F fixture row
The immutable OvenTemp lookup lists Gas Mark 6 as 200 °C and 400 °F. Use those values together when a recipe names Gas Mark 6. This agreement does not change the exact unit formula; it reflects the rounded Fahrenheit value chosen for that published Gas Mark row. A lookup is categorical: a nearby value does not become Gas Mark 6 automatically, and OvenTemp does not interpolate extra marks.
Fan guide: about 180 °C with recipe priority
The conventional-minus-20 guide changes 200 °C conventional to about 180 °C fan. Before applying it, verify that the original 200 value really refers to conventional mode. If the recipe already says fan, keep its stated fan setting. Watch high-sugar glazes, pastries, and small items that may brown quickly in circulating air. Follow recipe timing, appliance guidance, and food-safety temperature requirements rather than treating the subtraction as a universal law.