To convert 400 degrees Fahrenheit to Celsius, we can use the formula: T(°C) = (T(°F) - 32) × 5/9. Plugging in 400 for T(°F), we get:

T(°C) = (400 - 32) × 5/9 = 204.44°C

Therefore, 400 degrees Fahrenheit is equal to 204.44 degrees Celsius.