4 ms·

Any similar shortcut for feet inches to cm? I find this conversion to be slower to compute than miles to km or lbs to kg.

by xkgt 7y ago

ignoramous 7y ago
@sigfpe in a reply to the tweet mentioned Fₙ in ≈ Fₙ₊₂ cm https://twitter.com/sigfpe/status/1158465136891269121 https://twitter.com/sigfpe/status/1158465136891269121
cjbenedikt 7y ago
Fahrenheit to Celsius: (100F -30)/2= 35C
- achow 7y ago
  Not quite. It is 37.78. In temperature couple of degrees means a lot.
  - chrisdhal 7y ago
    For outside temperatures it's close enough though. As an American who travels to Central America quite a bit being about to do: (C*2) + 30 to get F is close enough.
- arcticbull 7y ago
  Just remember 100F was Fahrenheit's wife's body temperature when she had a low grade fever. Normal body temperature is 36.8C, and with a low fever it's between 37 and 38C. It's so easy! haha.
mhxion 7y ago
this was the size of my ruler: 12 inch ≈ 30 cm. therefore, 2 inch ≈ 5 cm
twic 7y ago
A metre is about 40 inches, and an inch is about 2.5 cm. So, first into total inches, then take out as many 40s as you can, then multiply what's left. 5' 7" -> 5 * 12 + 7 inches -> 67 inches -> 1 metre 27 inches -> 1 metre 67 centimetres Which isn't quite right, but is close-ish! And not really easy enough to call a shortcut either!
kurthr 7y ago
A yard is 0.9m. 1.1 yard per m or 1yd and 4in. A foot is 30cm. An inch is 2.5cm. 4in per 10cm. 2m is 6ft 8in =180+20=2m 5f 4in is 150+10=1.6m 1.6m is 3ft 4in + 24in=5ft 4in Even converting to and back isn't bad... work in a machine shop for a while and it will be second nature. Also metric/standard tools do not cross the line on the floor, only you and the work piece on different pieces of equipment. 25um looks like a mil, but it's not!
skykooler 7y ago
For inches to cm in my head, I multiply by 10 and then divide by 2 twice. E.g. 7 inches -> 70 -> 35 -> ~17.5 cm.
- frosas 7y ago
  I do something similar but, because I'm faster at multiplying, I do "its double plus its half". E.g. 7 inches = 14 + 3.5 = 17.5 cm
crdrost 7y ago
Yeah it's not actually that bad, the base-12 system helps you out. You multiply the feet by 3, divide the inches by 4, add, multiply by 10. Optionally add 1.5% to really get that extra precision. It's 30.5•(a+b/12) understood as about 1.015•10•(3a+b/4). So I am 6’4”, that becomes 18+1=19, so I am about 190cm. Adding between 1-2% gives me that I am between 192cm and 194cm. I know I am on the lower end of 6’4” (maybe 6’ 3.75”) so I usually report 192cm.

Any similar shortcut for feet inches to cm? I find this conversion to be slower to compute than miles to km or lbs to kg.

by xkgt 7y ago

Any similar shortcut for feet inches to cm? I find this conversion to be slower to compute than miles to km or lbs to kg.

ignoramous 7y ago

@sigfpe in a reply to the tweet mentioned Fₙ in ≈ Fₙ₊₂ cm https://twitter.com/sigfpe/status/1158465136891269121 https://twitter.com/sigfpe/status/1158465136891269121

cjbenedikt 7y ago

Fahrenheit to Celsius: (100F -30)/2= 35C

achow 7y ago
Not quite. It is 37.78. In temperature couple of degrees means a lot.
- chrisdhal 7y ago
  For outside temperatures it's close enough though. As an American who travels to Central America quite a bit being about to do: (C*2) + 30 to get F is close enough.
arcticbull 7y ago
Just remember 100F was Fahrenheit's wife's body temperature when she had a low grade fever. Normal body temperature is 36.8C, and with a low fever it's between 37 and 38C. It's so easy! haha.

mhxion 7y ago

this was the size of my ruler: 12 inch ≈ 30 cm. therefore, 2 inch ≈ 5 cm

twic 7y ago

A metre is about 40 inches, and an inch is about 2.5 cm. So, first into total inches, then take out as many 40s as you can, then multiply what's left. 5' 7" -> 5 * 12 + 7 inches -> 67 inches -> 1 metre 27 inches -> 1 metre 67 centimetres Which isn't quite right, but is close-ish! And not really easy enough to call a shortcut either!

kurthr 7y ago

A yard is 0.9m. 1.1 yard per m or 1yd and 4in. A foot is 30cm. An inch is 2.5cm. 4in per 10cm. 2m is 6ft 8in =180+20=2m 5f 4in is 150+10=1.6m 1.6m is 3ft 4in + 24in=5ft 4in Even converting to and back isn't bad... work in a machine shop for a while and it will be second nature. Also metric/standard tools do not cross the line on the floor, only you and the work piece on different pieces of equipment. 25um looks like a mil, but it's not!

skykooler 7y ago

For inches to cm in my head, I multiply by 10 and then divide by 2 twice. E.g. 7 inches -> 70 -> 35 -> ~17.5 cm.

frosas 7y ago
I do something similar but, because I'm faster at multiplying, I do "its double plus its half". E.g. 7 inches = 14 + 3.5 = 17.5 cm

crdrost 7y ago

Yeah it's not actually that bad, the base-12 system helps you out. You multiply the feet by 3, divide the inches by 4, add, multiply by 10. Optionally add 1.5% to really get that extra precision. It's 30.5•(a+b/12) understood as about 1.015•10•(3a+b/4). So I am 6’4”, that becomes 18+1=19, so I am about 190cm. Adding between 1-2% gives me that I am between 192cm and 194cm. I know I am on the lower end of 6’4” (maybe 6’ 3.75”) so I usually report 192cm.