Converting Celsius to Fahrenheit in your head easily.

Double the celsius number and subtract 10 % then add 32 and you have how many degrees fahrenheit it is.

I subtract the 10% from the doubled number after adding the 32 to it, I find that is easier to do in my head. Lots easier for me than the multiplying by 9/5 and adding 32.

Try a couple in your head, example:

20C = 20+20=40-4 (the 10%) =36+32= 68F

25C = 25+25=50-5=45+32=77F

33C = 33+33=66-6.6=59.4+32=91.4F

1C = 1+1=2-.2=1.8+32=33.8F

I find it easier to subtract the 10% of the 1st part after I add the 32, so in my head the last example would be 1+1=2+32=34-.2=33.8F

or 41+41+32=114-8.2=105.8F

Anyone else have a way to do it in their head beside the 9/5 way? If so, I would like to give it a try without pencil and paper too.

I'm not sure it is easier. Some people like the formula
F + 40 = 1.8*(C + 40), which is based on -40 F = -40 C.

Add 40 to the Celsius temperature
Use doubling, less 10% for the 1.8 factor
Subtract 40

23
63 +40
126 double
113.4 -12.6
73.4 -40

Yes, that works too fairly easily in my head. Thanks.