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# 5  The Travelers' Temperature Predicaments

Date: 05/12/2006

Temperature measurement is very important to a whole range of areas and activities: science, scientific research, manufacturing, medicine and travel. Many European, Asian and African businessmen and tourists often travel to the USA and UK. These countries have not adopted the use of the modern metric system of measurement i.e. the SI system.

The accepted base SI unit of temperature is the Kelvin. A change of 1K is the same as 1 degree Celsius. As the degree Celsius is a convenient, easy to grasp in every - day - life metric unit, therefore both units are used in parallel. The Kelvin is used by scientists and engineers and the degree Celsius by everybody else worldwide. There are however, two prominent exceptions: the USA and UK who commonly use the Fahrenheit scale.

Daniel, Gabriel Fahrenheit, a German physicist was born in 1686 in Gdansk, Poland. The concept of the thermometer for measuring temperature changes is credited to Galileo. Fahrenheit is known for inventing the alcohol and mercury thermometers. His temperature scale is based on affixing 32º for melting point of ice and 212º for the boiling point of water under normal atmospheric pressure. The interval between two affixed points is being divided into 180 equal parts (the degrees Fahrenheit). The Fahrenheit scale was generally in use by English speaking countries up until 1970. Travelers to the USA and UK are often faced with the problem of how to efficiently convert the temperature in the degree Fahrenheit to the temperature expressed in the degrees Celsius without making a mistake and with a sufficient approximation.

The conversion formula "Fahrenheit to Celsius" is:

ºC = 5/9 (ºF - 32º); read:

"In order to express the temperature in the degrees Celsius, I need to divide 5 by 9 and the result multiply by the temperature in Fahrenheit lowered by 32º".

Quite awkward, isn't it?

A much simpler way to remember and easier method to do mentally is to memorise the four following steps:

ºF→→→ºC : "Subtract 32, divide by 2, add 10% ( or 1/10) of the result and add 1% of the total".

Let us see how it works:

E.g. 1: 98 ºF (your normal body temperature) →→→66 →→→33 →→→36.3 →→→36.7 ºC (rounded off to one decimal place).

E.g. 2: 102 ºF (your possible body temperature) →→→70→→→35→→→38.5→→→38.9 ºC

(High, pay a visit to the doctor!).

E.g. 3: 68 ºF (pleasant, refreshing outdoor temperature)→→→36→→→18→→→19.8→→→20 ºC

If you in a good mood, hum these four steps before the travel: "su-di-a-a", "su-di-a-a", "su-di-a-a"...!

Have a nice trip and keep warm!


PS.: Have you read my former article: "The Travelers Temperature Tips"?

If so, you will be able to find the answer to the following puzzle:


A student solving a problem on transfer of heat found a correct temperature change. However, he presented the answer without a unit. As it turned out, it did not matter whether he gave the temperature in the degrees Fahrenheit or the degrees Celsius. The answer remained the same. What temperature was it?


Do you like anecdotes, interesting and challenging problems, fun facts, puzzles, jokes related to metric system and measurement? Read them in the 2015 on-line edition of "SI Units, Conversion and Measurement Skills",204 pp.