Formula:

Celsius = (Fahrenheit - 32) * 5 / 9

Calculation:

1. Subtract 32 from the Fahrenheit temperature: 103.6 - 32 = 71.6

2. Multiply the result by 5: 71.6 * 5 = 358

3. Divide the result by 9: 358 / 9 = 39.78

Therefore, 103.6 degrees Fahrenheit is approximately 39.78 degrees Celsius.