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Fahrenheit is a temperature scale named after a German physicist called Daniel Gabriel Fahrenheit who developed the idea in 1724. It was the normal scale for measuring temperature in most English-speaking countries until the second half of the twentieth century. In 1965, the UK government announced its intention of changing all weights and measures in the country from the former imperial system to the metric system, a change which has yet to be completed. In the measurement of temperature, there was international agreement in 1948 that the Celsius scale should be used. It is still not always used in the UK. Although all scientists now should use nothing but centigrade, older people will normally refer to the weather, where 70°F is a very pleasant summer's day, and blood temperature, 98°F, in terms of Fahrenheit. In the United States, the Fahrenheit scale is still the norm, outside scientific writing.

In the Fahrenheit scale the boiling point of water is 212 degrees and the freezing point 32 degrees - exactly 180 degrees apart. The unit of this scale - one degree Fahrenheit - is equal to five ninths of a degree Celsius and absolute zero is at -459.67°F. The Fahrenheit scale was the primary temperature standard for climatic, industrial and medical purposes until the 1960s. Then, in the late 1960s and 1970s, the Celsius scale was introduced by governments as part of the standardizing process of metrication.

To convert degrees Fahrenheit (°F) to degrees Celsius (°C), use the formula °C = (°F - 32)/1.8. To convert the other way, use the formula °F = 1.8(°C) + 32. This information may help students who use older texts, in History and literature for example. But students in Higher Education in the UK, are advised to use Celsius unless there is a good reason for using otherwise. (Such a good reason, of course, might be available to those physical scientists who want to use the Kelvin scale, or engineers who need the Rankine scale.)