18 degrees Celsius is equal to 64.4 degrees Fahrenheit. To convert Celsius to Fahrenheit, the formula is F = (C × 9/5) + 32, where F is the temperature in Fahrenheit and C is the temperature in Celsius. Plugging in 18 for C, we get F = (18 × 9/5) + 32 = 64.4, which is the temperature in Fahrenheit.