Metric Temperature Conversion
Changing from Fahrenheit to Celsius and Kelvin
The basic formulas to use when converting temperatures between Fahrenheit, Celsius and Kelvin.
There are three different scales used to measure temperature, and there are basic formulas to convert temperatures in one scale to the equivalent degrees in the others.
The Three Temperature Scales
The key points for measuring temperatures in each of the scales are based on the freezing and boiling temperature of water at sea level.
All the scales are linear, that is, the degree points are divided evenly; there is the same difference in temperature between each point on the scale.
The Fahrenheit scale (F.), used in the United States, sets zero degrees at an arbitrary point. The temperature at which water freezes is at 32 degrees, and the boiling point at 212 degrees.
The Celsius scale (C.) sets zero at the freezing point of water. It is also referred to as the Centigrade scale because the boiling point of water is set at 100.
The Kelvin scale fixes zero at absolute zero, theoretically the coldest possible point, where all motion stops. Counting up from there, the Kelvin scale uses the same measurements as the Celsius scale.
Converting from Celsius to Fahrenheit
Since the base point of freezing for Fahrenheit is set 32 degrees higher than Celsius. The first step in the formula is to subtract 32 degrees. The next step is to convert any degrees above or below 32 to Celsius.
A Celsius degree is larger than a Fahrenheit degree. It is exactly 9/5 greater, so that for every five degree increase in Celsius, there is a nine degree increase in Fahrenheit.
For example, to convert 10 degrees Celsius, multiply 10 by 9/5 and add 32. The result is 18 plus 32 = 50. In the same manner 20 C. equals 68 F. and 30 equals 86.
The formula is Fahrenheit = Celsius x 9 / 5 + 32.
Converting Fahrenheit to Celsius
The formula works similarly in for converting back to Celsius. Subtract 32 from the Fahrenheit reading and divide by 5/9. Make sure to subtract 32 before dividing, or you will end up with the wrong result.
For example, to in converting 50 degrees Fahrenheit to Celsius, subtract 32 from 50 = 18 divided by 9 = 2 times 5 = 10 degrees Celsius.
By using the formula, it can be determined that -40 degrees is the point where Fahrenheit temperature is equal to Celsius.
Converting to Kelvin
The Kelvin scale is used mostly in scientific applications. It uses the same degree widths as Celsius, so the conversion from Celsius can be easily done by adding approximately 273 degrees to the Celsius temperature. NASA fixes the number at 273.15, although other sources use a slightly different number.
For example, 10 degrees Celsius equals 283 degrees Kelvin. In converting from Fahrenheit, follow the formula for converting to Celsius and then convert to Kelvin.
