To convert temperatures from Fahrenheit to Celsius, subtract 32, multiply the difference by 5, and then divide the product by 9. To convert from Celsius to Fahrenheit, reverse the formula. Both temperature scales are linear, but the slopes (the numerical change per change in heat energy) are different.Continue Reading
Take the reading from a Fahrenheit thermometer, and subtract 32. Multiply that answer by 5, and divide the result by 9 to yield the Celsius equivalent. Consider the example of 212 degrees Fahrenheit. Subtracting 32 yields 180, multiplying by 5 yields 900, and dividing by 9 yields 100. Remember that the boiling point of water is 212 degrees Fahrenheit or 100 degrees Celsius, meaning that these two numbers reflect the same amount of heat energy at work.
Consider a thermometer reading of 0 degrees Celsius. Multiply by 9 to remain at zero; divide by 5 to remain at zero; add 32 to yield 32 degrees Fahrenheit. Remember that both of these temperatures reflect the heat energy present at the freezing point of water.
Use the Celsius-to-Kelvin conversion in scientific applications when dealing with extremely low temperatures. Remember that multiplication and division are necessary when converting from Celsius to Fahrenheit and back because the amount of heat energy change per degree is different. Add 273.15 to any Celsius reading to yield the temperature in Kelvin, because the heat energy change per degree is the same for both scales.