Converting Temperatures

One of the challenges in moving from America to England is switching from Fahrenheit to Celsius. The two main challenges are cooking and dressing for the outdoor weather.

Cooking hasn't been so bad. In addition to having a book with standard temperature conversions, we also have a little sheet taped up on the side of the oven with the conversions from Fahrenheit to Celsius. Gas marks are also a popular way to set the temperature on ovens, so the chart also lists "gas mark 2, gas mark 3, etc."

More problematic is the weather. My wife heard a little rhyme to help with knowing how to dress:

30 is hot, 20 is nice,
10 is cold, 0 is ice.

While this is generally helpful, one wonders where, for example, 17 falls in the shirt-sweater-coat-parka spectrum. The formula for the conversion is F=(1.8*C)+32. Multiplying 17 by 1.8 isn't so easy off the top of one's head, so I've been trying to figure out an easier way to make the conversion.

I realized that for every 10 degrees of Celsius, Fahrenheit goes up 18 degrees. Thus the rhyme above converts to this:

30 is 86 degrees, 20 is 68,
10 is 50, 0 is 32.

Doesn't really rhyme but it is an easier scale to map against a personal shirt-sweater-coat-parka spectrum. Because, let's face it, coat weather for one person can be just shirt weather for another person. If you doubt that, come here and see the people running around in varying states of dress on a sunny, 24 degree Celsius day.

Also, I think the numbers are easier to memorize than they first appear. 86 is 68 backwards, 50 is pretty easy to remember, and I think everyone knows freezing is 32 F and 0 C.

Finding numbers in between isn't too hard, either. One just remembers that every 10 degrees Celsius is 18 Fahrenheit. So if a temperature ends in 5, just take half of 18 and add 9 to 86, 68, 50, or 32. If the temperature is over 35 Celsius, it is way too hot to be outside without a cold beverage. At least on my personal shirt-sweater-coat-parka spectrum.

With a few tricks, converting temperature is as easy as Pi!