Just when we thought we had seen the last of Fahrenheit temperatures, a tabloid headline warns us against complacency and reminds us of those awkward conversions. Awkward no more, we are pleased to say, as Metric Views has learnt of a simple formula.
Headline from the Sunday Express on 5 April:
BRITAIN is about to get a long-awaited taste of summer with blue skies, sunshine and temperatures nudging 70F this week.
The Celsiheit thermometer immediately came to mind:
Interestingly, the internet version of the same paper had this headline:
Britain gets a blast of summer sun: Next week to bring blue skies and 21C.
Readers are invited to speculate on the reasons for the difference.
Of course, UKMA has always urged “Think metric. Don’t convert.” But there may be occasions when a conversion between C and F makes life easier, for example when the in-laws are over from the USA and can’t decide what to wear, when the kids can’t understand a tabloid headline, or when grandma insists on passing on a favourite cookery recipe.
For such circumstances, we can recommend this conversion formula, which was passed on to us by a contact in Canada, Alan J. Nanders. It is memorable, and the arithmetic is straightforward.
For almost 50 years, I have been the lone voice in North America teaching the simple and easy-to-remember formula for accurately converting Fahrenheit temperatures to Celsius or Celsius to Fahrenheit. It is elegant in its simplicity, while totally avoiding the conundrum of when to add and when to subtract that confusing 32 degrees.
My “Nanders formula” is accurate for all values of conversion. Moreover, steps 1 and 3 are identical, regardless of which way you convert.
HERE IT IS:
Step 1. Add 40
Step 2. Multiply by 5/9 (F to C) or 9/5 (C to F)
Step 3. Subtract 40
So how long are we likely to be converting from C to F or vice versa?
The UK Met Office adopted metric measures for internal use early in the twentieth century, but the BBC did not include Celsius (then known as centigrade) in its public forecasts until 1962. On the other hand, the USA shows no sign of nearing the end of its 150 year-long changeover to metric measures, and there are few Celsius temperatures in US forecasts. So the Nanders formula could be helpful for some time to come.
Alan has a fund of stories about metrication in Canada and some these will be the subject of a future article on Metric Views.
For the rational proof or explanation of the formula, contact firstname.lastname@example.org.