Ever want to be able to convert from Celsius to Fahrenheit quickly and easily? There are two easy methods, one made by my late Uncle Gene, which results in a close approximation of the Fahrenheit. In his honor I call this unit of measure a Geno, his nickname.

It's really easy! Multiply the Celsius by 2 then add 30. So simple! This is accurate enough to easily answer the question, "Should I wear a sweater or a t-shirt today?" Here are a few examples:



Celsius.....................Geno........Fahrenheit
-20 x 2 = -40, + 30 = -10...........-4
-15 x 2 = -30, + 30 = 0...............5
-10 x 2 = -20, + 30 = 10............14
-5 x 2 = -10, + 30 = 20..............23
0 x 2 = 0,,,,, + 30 = 30..............32
5 x 2 = 10,,, + 30 = 40..............41
10 x 2 = 20, + 30 = 50..............50
15 x 2 = 30, + 30 = 60..............59
20 x 2 = 40, + 30 = 70..............68
25 x 2 = 50, + 30 = 80..............77
30 x 2 = 60, + 30 = 90..............86
35 x 2 = 70, + 30 = 100............95
40 x 2 = 80, + 30 = 110...........104

Simply go in reverse if you start with Fahrenheit, but want the Celsius. Couldn't be easier.

However, for those of you who feel that 77 degrees is comfortable, but 80 makes you sweat, then Genos aren't accurate enough. Let's see the easy way to convert Celsius to Fahrenheit. In grade school I learned that 9/5ths of the Celsius plus 32 equals Fahrenheit. In college the professors simply used 1.8 instead, since 1.8 equals 9/5ths. But, that only helps speed things up if you have a calculator.

Thankfully, I learned a long time ago that there are tricks to do this type of math in your head. Applying this method to the Celsius~Fahrenheit fiasco and we see that 1.8 is 20% less than 2. Or, said more consistently, 1.8 is 0.2 less than 2. This makes the math easier.

Multiply the Celsius by 2, and remember that as result 1. Then, divide this by 10, and remember that as result 2. Simply subtract the second result from the first result, and we have a third result, the same as if we had multiplied 1.8 times the Celsius.

Now we take the third result and add 32. Here are a few examples:

C x 2 = R1, R1/10=R2, R1 - R2 = R3, R3 + 32 = Fahrenheit
-20 x 2 = -40, -4, -40-(-4) = -36,,,,,, -36 + 32 = -4
-15 x 2 = -30, -3, -30-(-3) = -27,,,,,, -27 + 32 = 5
-10 x 2 = -20, -2, -20-(-2) = -18,,,,,, -18 + 32 = 14
-5 x 2 = -10,,, -1, -10-(-1) = -9,,,,,,,, -9 + 32 = 23
0 x 2 = 0,,,,,,,, 0,,,,,,, 0 - 0 = 0,,,,,,,,,, 0 + 32 = 32
5 x 2 = 10,,,,,, 1,,,,, 10 - 1 = 9,,,,,,,,,,, 9 + 32 = 41
10 x 2 = 20,,,, 2,,,,, 20 - 2 = 18,,,,,,, 18 + 32 = 50
15 x 2 = 30,,,, 3,,,,, 30 - 3 = 27,,,,,,, 27 + 32 = 59
20 x 2 = 40,,,, 4,,,,, 40 - 4 = 36,,,,,,, 36 + 32 = 68
25 x 2 = 50,,,, 5,,,,, 50 - 5 = 45,,,,,,, 45 + 32 = 77
30 x 2 = 60,,,, 6,,,,, 60 - 6 = 54,,,,,,, 54 + 32 = 86
35 x 2 = 70,,,, 7,,,,, 70 - 7 = 63,,,,,,, 63 + 32 = 95
40 x 2 = 80,,,, 8,,,,, 80 - 8 = 72,,,,,, 72 + 32 = 104


How about going from Fahrenheit to Celsius using this method? Firstly, subtract 32 from the Fahrenheit to get result 1. Then multiply result 1 by 10%, or divide by 10, and that is result 2. Round result 2 up to the nearest whole number. Add result 2 and result 1 to get result 3. Divide result 3 by 2 for a very close approximation of the Celsius.

Fahrenheit - 32 = R1, R1/10=R2, R1+R2=R3, R3 / 2 => "Celsius"
104 - 32 = 72, 72/10= 7.2 -> 8, 72+ 8=80, 80 / 2 => 40
68 - 32 = 36, 36/10= 3.6 -> 4, 36+ 4=40, 40 / 2 => 20
20 - 32 = -12, -12/10=-1.2 -> -2, -12+(-2) = -14, -14 / 2 => -7