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News you can use: How to handle numbers like a true nerd

Published on 30 Comments on News you can use: How to handle numbers like a true nerd

The previous post reminded me of something that a few of you might find useful: a way of remembering certain facts and figures that are often hard to keep in mind. I first starting using this years ago to convert temperatures from Celsius to Fahrenheit. The problem is that most metric conversions have fairly easy approximations:

But not temperature. Celsius has a complicated conversion formula that few of us can calculate on the spot. So instead just try to remember a few easy numbers:

Use these approximations for ten-degree Celsius intervals and you know everything you're likely to need unless you design thermostats or work on the Mars Rover.

Here's one for inflation:

Inflation has doubled since 1995 and gone up 10x since 1965. Here is family income:

The key here is to be happy with rough approximations and to choose only three or four easy data points to remember. Maybe someday I'll make a whole book of these handy conversions.

30 thoughts on “News you can use: How to handle numbers like a true nerd”

  1. dspcole

    Does the “Family Income in America” refer to North America or South America? Canada or just the US? All of these posts are getting me so confused

    2. AnnieDunkin

      My buddy's mother makes $50 per hour working on the computer (Personal Computer). She hasn’t had a job for a long, yet this month she earned $11,500 by working just on her computer for 9 hours every day.

      Read this article for more details.. https://payathome.blogspot.com/

  3. barleyfreak

    Long ago a friend told me to get a quick approximation of F from C is *2+30. it works pretty well in most of the range one finds themselves.

    1. J. Frank Parnell

      For temperature, times 2 minus 10% +32 is exact. T °F = (T°C) x 9/5 +32

      For distance, L (m) = L (yards) + 10% is very close, within 0.6%.
      Likewise, for distance L(in) = L (cm) x .4 (within 1.6%)
      And mass (or force), M (lbs) = 2 x M(lbs) +10% (within 0.21 %)

      1. cld

        But that's not actually easier to do in the head than multiply by 1.8 and add 32.

        My head, anyway. Which I don't deny may be a poor example.

        1. J. Frank Parnell

          I find it easier to. double the temperature (30 becomes 60), subtract 10% (60 - 6 = 54) and add 32 (54+ 32 = 86).

      2. Altoid

        And for bigger distances a kilometer is almost exactly 5/8 of a mile, so 5/8 and 8/5 are a handy way to convert mph and kph. For those who occasionally like to do math in their heads, and/or don't have siri or alexa on call . . .

    2. Jasper_in_Boston

      My personal formula for doing the mental conversion: "Add a bit less than double the Celsius total to 32." Seems to work with reasonable accuracy.

    1. Jasper_in_Boston

      The metric system is widely used in the United States. At this point the country isn't hampered in the least by the limited number of English measurement legacies (miles, pounds, feet/inches, Fahrenheit).

  5. lawnorder

    Those are EXTREMELY rough approximations, especially 1km= o.5 miles. A kilometer is 25% longer than a half-mile. Is five-eighths really that hard to work with?

  6. dilbert dogbert

    Nurdy me: The inch was redefined as a nice two place decimal!!! 2.54 cm per inch. Close enough for government work.

    1. rich1812

      Vertical axis is CPI and not inflation, which would be the percentage change in a price index like the CPI. And on the horizontal axis, the numbers relative to inflation should be reduced by 1. From '95 to today we have roughly 100% inflation and prices have roughly doubled. Inflation has not doubled since '95. Prices have roughly doubled. The average inflation rate has been about 2.5% (1.025)^27 roughly equals 2.

      I expect better of you Kevin! 🙂

    2. Jasper_in_Boston

      Yeah, I thought that was weird, too. An uncharacteristically, uh, non-pristine use of language by Kevin Drum. He should have written "prices have gone up" instead of "inflation has gone up."

  8. Bill Camarda

    How I was taught to handle Celsius:

    "30 is hot, 20 is nice,
    10 is cool, Zero is ice."

    But in the era of global warming, I've started to hear:

    "Ten is cold; 20's not;
    30's warm; 40's hot."

  9. MrPug

    Sorry Kevin, but km to miles is much closer to 2/3 than 1/2. It's something like 0.62 km to miles. so, a 10k run is roughly 7 miles not 5. A 5k is basically 3 miles not 2.5.

    And F to C is pretty easy. F is roughly 2(actually 9/5's) *C + 32. So, 10 degrees C is a bit less than 50 degrees F.

    I also find it easier to think of an inch being roughly 2.5 cm. Also because 1 in is 0.4 cm which is pretty far from 0.5.

    So your "estimates" are going to get people pretty far off the mark. And I think simple-ish fractions are easier than attempting to interpolate as you did with F C.

  10. pjcamp1905

    I remember:

    1. 9/5 (or 5/9)
    2. Celsius degrees are bigger so there are fewer of them.
    3. When you're in Fahrenheit, adjust by 32.

  11. Displaced Canuck

    Canadian using metric and not caring about imperial (what we call the old system). However, I'm also British and lived in Scotland from 2010 to 2020 and they half converted to metric so you need to know the approximate conversions. I also agree Kevin's worse suggestion was kilometres to miles. 5/8 or even 2/3 is much closer and still easy.

    1. Jasper_in_Boston

      You have to be right. No way fully a fifth of US families are earning north of 300 grand. Maybe Santa Clara County or even OC. But the US as a whole?

  13. dmcantor

    Do me a favor: Instead of saying "Inflation has gone up by...," say instead "Prices have gone up by...." You can say "Average prices..." if you need to. This will stop the moans of dismay emanating from Edgewater, MD.

  14. Scott Martin

    This reminds me of an old SCTV sketch where Canadians Bob & Doug McKenzie are discussing the metric system:

    "OK, metric's easy, eh? Double it, add 30, you've got metric."

    "So what would a six pack be in metric?"

    "OK, so double it , it's 12, add 30 ... ho, 42 beers!"

    "Count me in on metric, eh?"

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