Fahrenheit to Celsius calculation

Fahrenheit to Celsius calculation

There are two scales used in the calculation of Fahrenheit to Celsius. The Celsius scale °C is a part of the Metric system that is used in most countries while the Fahrenheit scale °F is mostly used in the US to denote temperature readings. Both scales are used to measure temperature. However, they use different numbers when showing the temperature reading.

For example, the water freezes at a temperature reading of 0° Celsius and is shown as 32° Fahrenheit. Boiling water at normal pressure will click a reading of 100° Celsius and will be indicated in Fahrenheit as 212° Fahrenheit. Since the scales start at different numbers, we will either add or subtract by 32. The fact that they rise at different rate means that we should multiply to get the other reading. The Celsius scale will have a difference of 1000 while the Fahrenheit scale will have a difference of 180.

To determine the calculation of the two scales;

100/180 can be simplified as 5/9 whereas 180/100 can be simplified as 9/5.

The fastest way of converting °F to °C will be; deduct the temperature reading in Fahrenheit by 32 and then multiply by 5/9.

T (°C) = {T (°F) – 32} x 5/9 is the method used in the calculation. It can be simplified further and written as;

T (°C) = {T (°F) – 32} / 9/5


T (°C) = {T (°F) – 32} / 1.8

For example;

Convert 68 degrees Fahrenheit to degrees Celsius


T (°C) = {T (°F) – 32} x 5/9


T (°C) = 68 °F – 32} x 5/9

= 20 °C

Other methods that work

First, add 40 to the temperature reading in Fahrenheit. Multiply the result by 5/9 and then subtract 40.


Convert 68 degrees Fahrenheit to degrees Celsius


68 + 40 = 108

108 x 5/9 = 60

60-40 = 20 °C