Celsius to Farenheit

That's too much for me! I just double and add 30. If it's before 0, we are usually at home.

Just google ?? F to C or vice versa.

I use an app.

My new smartphone displays the outside temperature in F regardless of where I am.

Without reading the article, my easy way to remember is that 28C is 82F. This helps me to gage the weather. Above 28 it is hot. Below it is a little cooler.

For me, an easy additional reference point is body temperature: 37 degrees celsius is practically 100 degrees fahrenheit (too hot for me, if it relates to weather!!).

Double it, subtract 10% (is there anything easier do in the head than double or than 10%?), and add 32.
Really simple, and if this is too much math then you didn't graduate high school.
Why was that article even written?

This only works in this temp range, but 10C is 50F and 20C is roughly 70F. Obviously 0C is 32F

Another easy reference point: 16 C. = 61 F.

When oh when will the U.S. join the world?

The calculator app on my android phone has a conversion option for all metric to imperial measurements.

The easiest way for me to do a quick mental conversion is that I have memorized 4 points:
0 C = 32 F (freezing)
10 C = 50 F
20 C = 68 F (room temperature)
30 C = 86 F (flip the 6 and 8 from room temp)

Simply posted the link for the benefit of anyone would want to use the method of rough approximation detailed. It's very simple (similar to Laura's method), and requires no math, app, or anything - just a little memory. Everyone has their own method, and that's fine; whatever floats the boat. Personally, with seven and a half year of university training, I just do the math conversion in my head as it helps keep me mentally sharp in my so called doatage. No need for snarkiness.

Multiply by 2, subtract 10%, add 32. Do it in your head. It's good to practice.

30 C - 60 F - 54 F - 86 F

40 C - 80 F - 72 F - 104 F

Thanks, TC!
Read and appreciated.

I have to laugh because being a child of the 1970s and early 1980s, in elementary school we were taught about the metric system and Celsius conversion. Our teacher and the film we watched promised that by the advent of the 21st century, the metric system would be in use across America and we would have to know it. Of course, it never happened and non-use plus the advent of smartphones meant I've forgotten most of it.

It becomes really acute when trying recipes from outside the US and having to convert grams to cups/tsbs, etc. Thank goodness for my kitchen scale. But again, the US is behind. Maybe the US can try for the 22nd century to get in line with the world.

When oh when will the U.S. join the world?

When oh when will the world start using the metric system - all of it?

It's a not-well-known fact that "the world" only uses 2/3 of the "metric" system. If the metric system is so great, why doesn't the world use all of it?

Yes, the metric system, as originally devised, was comprised of three basic measurements - length, mass, and time, MKS (Meters, Kilograms, & Seconds), and all three measurements were decimalized.

How many people carry around a device for measuring length, like a meter stick? Oh, at 39.4 inches (approx), a meter stick would be pretty awkward to carry around. How about a 15cm stick? That's 5.9 inches, about the same length as a 6" rule. How many people, other than engineers, carry around a 6" rule in their pocket?

Or mass? How many people carry around a balance and weights to measure mass? Nobody. Some people might carry around a spring scale, which measures weight (force), not mass, and since the acceleration of gravity varies by location, weight is only an estimation of mass. But still, very few people carry around a device to measure weight.

How many people have on their person a device to measure time? It might be an old fashioned watch, with hands, or, more likely, you use your cell phone. Answer: almost everyone carries around a device to measure time. Time is, by far, our most commonly used measurement, or metric.

How many seconds in a minute? 60! How many minutes in an hour? 60! How many hours in a day? 24! Why isn't time decimalized?????

Most of you people didn't know, until I just told you, that the metric system, as originally devised, had all three measurements decimalized. There were 10 metric hours in a day, 100 metric minutes in an hour, and 100 metric seconds in a minute. That's 100,000 metric seconds in a day versus 86,400 non-metric seconds in the system we use.

So what happened to metric time? Why isn't it used today? People didn't like it, so they didn't use it.

So, how many hours, minutes, and seconds between, say, 9:41:23am and 6:23:45pm (or 18:23:45)? In metric time, that would be a piece of cake. Just subtract. But in what is today's "metric" time, you have to multiply the hours times 3600, and the minutes times 60, add them together to get the difference in seconds, then divide by 60, and 3600 to get the hours and minutes.

Time is the most often used measurement, yet we don't use a decimalized (metric) version of time, because it isn't convenient.

If the US is ever going adopt a different system, we should adopt the ideal (full) metric system, not just 2/3rds of it, and insist that rest of the world join "the World", too.

I feel bad for the OP. Why bother trying to be helpful after that rant?

To help the OP, I'm expanding on what Laura posted,

0° C = 32° F (freezing)
10° C = 50° F (cool day)
20° C = 68° F (room temperature)
30° C = 86° F (warm day)
40° C = 104° F (hot day).
For every °C above or below the above temperatures, you just add or subtract 1.8°F, i.e., 21°C is 69.8°F.

My previous post was not a rant, it was a purely objective analysis of the SI system, and it's weaknesses. Other posters seemed to think we should switch to it just because "everyone else" is using it. I would be willing to switch if we actually switched to a system that was optimized. The current SI system is not.

The meter was supposed to be 1 ten millionth of the distance from the No. Pole to the equator on the meridian that passes through Paris, the so-called "Rose line". But they missed the meter length by .22"(0.56 cm). So the meter now is just a rod of platinum-iridium in a temperature controlled room in Paris. It could just as easily been a foot long, or a yard long. Or, preferably, it should be 36.606 inches long, in which case g, or gravitational acceleration, would have been 10 m/sec².

Why would that be important? The weight of a 1 kg weight is mass x g (1 kg x 9.8m/sec²) or 9.8 Newtons (of force). Had the meter been 2% shorter, it would be easy to convert kg to Newtons, just multiply by 10, or move the decimal. Isn't that what's supposed to be so great about the metric system, that all measurements are just a multiple of ten apart?

[And yes, I know that g is not the same at every point on earth, but scientist now use the approximation of 9.8 to calculate the weight in Newtons. Rarely do they need to apply the actual value of gravitational acceleration at their location.]