The Fahrenheit scale was created by a German physicist named Fahrenheit in the 18th century, although it was later modified by other scientists. On the Fahrenheit scale, zero is the temperature of a brine solution. The 100 degree point was once set as the temperature of a human body, but this was later changed to make the freezing and boiling points of water exactly 180 degrees apart, at 32 and 212 degrees Fahrenheit. A single degree on the Fahrenheit temperature scale is equivalent to 5/9th of a degree on the Celsius temperature scale.
The Celsius temperature scale was named after an astronomer of the same name who created a temperature scale based on the melting and boiling points of water, although the direction of his scale was then reversed by other scientists to its modern direction. The zero point of the scale is the freezing or melting point of water, while water's boiling point is at 100 degrees Celsius.
The Kelvin temperature scale was named for the physicist Lord Kelvin, who was the first to suggest that there was a lower limit to temperature, which is known as absolute zero. It is impossible to have a temperature that is colder than absolute zero. Absolute zero is the starting point of the Kelvin scale. A single Kelvin unit has the same magnitude as one degree Celsius.
Conversions
Whenever the need to convert temperature from one scale to another arises, you can use the conversion formula, or use the instant temperature converter to convert temperature from Celsius to Fahrenheit, Kelvin and Rankin.
To convert between temperature scales it is necessary to account for the differences between the starting points on which the scales are based as well as the differences between the magnitudes of the units that are used. The equations for temperature conversions, where C = temperature in degrees Celsius, F = temperature in degrees Fahrenheit and K = temperature in Kelvin are as follows:
C = (F -32) x 5/9
F = C x 9/5 + 32
C = K - 273.15
K = C + 273.15
F = K x 9/5 - 459.67
K = (F + 459.67) x 5/9
Example Conversions
1. A cook is reading a recipe that calls for the oven to be turned on at 450 degrees Fahrenheit, but their oven dial needs to be set using measurements in degrees Celsius. In order to set the oven to the right temperature and cook the dish properly, the cook needs to convert the temperature into Celsius.
To convert a temperature from Fahrenheit into Celsius, it is necessary to subtract 32 and then to multiply by 5/9.
The cook begins by subtracting 32 from 450, to make 418. Next, they multiply this by 5/9 to make 232.22.
450 degrees Fahrenheit is equivalent to 232.22 degrees Celsius.
The oven dial needs to be turned to 232 degrees Celsius in order to cook a dish at 450 degrees Fahrenheit.
2. An American tourist is visiting Europe. Before leaving the US, the tourist checks the weather report for their destination and finds that the temperature is expected to be about 30 degrees during their stay. If the tourist assumed that these temperatures were given in Fahrenheit, they would assume that the weather was going to be cool. However, the tourist luckily recognizes that the weather report is given in degrees Celsius. In order to know what temperatures to expect so that they can pack appropriate clothing, the tourist needs to convert the temperature into Fahrenheit.
To convert a temperature from Celsius into Fahrenheit, it is necessary to multiply by 9/5 and then to add 32.
The tourist begins by multiplying 30 by 9/5 to make 54. They then add 32 to make 86.
30 degrees Celsius is equivalent to 86 degrees Fahrenheit.
The tourist realizes that the temperature at their destination will actually be hot and they are, therefore, able to pack the right clothes for their trip.
3. An international team of scientists is working on a project during which they need to make very accurate measurements of temperatures. If their measurements are even a tiny bit wrong then it could ruin the whole project. The team is using an instrument that can measure temperatures in Kelvin.
The teams take a temperature measurement of 25 Kelvin. They use this scientific measure in their calculations and reports, but they also choose to calculate what this temperature means in scales with which they are more familiar in their everyday lives. This makes it easier for them to understand the temperatures they are talking about and it also makes it easier for them to communicate their findings to the media and non-scientists.
Some of the scientists prefer to use the Celsius scale, but others are more familiar with the Fahrenheit scale.
In order to convert the measurement from Kelvin into Celsius, it is necessary to subtract 273.15.
The scientists subtract 273.15 from 25 to make -248.15 degrees Celsius.
In order to convert the measurement from Kelvin into Fahrenheit, it is necessary to multiply by 9/5 and then to subtract 459.67.
The scientists multiply 25 by 9/5 to make 45. They then subtract 459.67 to make -414.67.
The measurement of 25 Kelvin is equivalent to -248.15 degrees Celsius or -414.67 degrees Fahrenheit.
When the scientists show their findings to non-scientists, their audience is much more familiar with the Celsius and Fahrenheit scales, so they are able to understand how cold this temperature is thanks to the conversion.
Estimating
Rather than performing an exact calculation, it is also possible to estimate a conversion between the Fahrenheit and Celsius temperature scales. The temperature in Fahrenheit is approximately double the temperature in Celsius, so to estimate a conversion between then it is possible to simply double or halve the temperature. This method is most useful when cooking.