A Fahrenheit User’s Guide to Understanding Celsius

Despite all my gradeschool teachers telling me to get ready because the metric system was coming (this was back in 1980), the United States still uses Fahrenheit to tell temperature.

The rest of the world, however, uses Celsius. So a few months back, I started thinking in Centigrade.

The “official” formula to convert between Fahrenheit and Celsius is sort of complex for on-the-fly conversions:

[°C] = ( [°F] - 32 ) × 5/9

Maybe some people can easily multiply by 5/9 without a calculator, but I'm not one of them. But there's an easier method, and it's one most people can determine relatively quckly:

[°C] = [°F]-30/2.

So if it's 70°F, it's 20°C. [ 70-30 = 40. 40/2 = 20 ]

This isn't an exact conversion (the official conversion puts 70*F at 21.1*C), but it's close enough to know if you need a jacket or a T-shirt.

Here's what you need to know about Celsius.

• 0: Cold. Jacket required. And maybe some layers.

• 10: Chilly. A jacket is a good idea.

• 15: Cool. You might want to bring a jacket just in case.

• 20: Temperate. No jacket necessary unless you get cold easily.

• 25: Warm. You should be fine in a T-shirt.

• 30: Hot. Definitely T-shirt weather.

• 40: Very hot. Stay inside.

There you have it. A simple way for those of us raised on Fahrenheit to gauge the temperature in Celsius.

Header image: Thermometer. Photo by from the author’s collection.