Use memorized comparison points to convert between the two systems if only an approximation is needed. A short and easily memorized rhyme can help persons who are familiar with Fahrenheit but not Celsius. The rhyme states, "Thirty is hot, 20 is nice, 10 is cold and zero is ice." It can help people remember that the 80-degree F range like a warm summer day will be around 30 degrees Celsius. Other comparison points to memorize include the freezing and boiling points of water and normal human body temperature, which is approximately 98.6 on the Fahrenheit scale and 37 degrees on the Celsius scale.
Convert degrees Celsius to degrees Fahrenheit using the math formula of degrees (Celsius x 1.8) + 32. After multiplying by 1.8, adding 32 to the answer accounts for the freezing temperature of water being 0 in the Celsius system and 32 in the Fahrenheit system. As a rule, comparable temperatures will be expressed in larger numbers in the Fahrenheit system (except for some below-freezing numbers).
Convert degrees Fahrenheit to degrees Celsius by using the following math formula: (degrees Fahrenheit - 32) x 0.555. Equivalent temperatures generally will be smaller numbers in the Celsius system.