4 ms·
I use a similar method of easy-to-remember numbers in conversion between celsius to Fahrenheit: 0 = 32 10 = 50 20 = 68 30 = 86 Then roughly, subtract/
by magoon 7y ago
I use a similar method of easy-to-remember numbers in conversion between celsius to Fahrenheit:
0 = 32
10 = 50
20 = 68
30 = 86
Then roughly, subtract/add two F for every extra C. It’s easy to remember 32 and 50, while 68 and 86 are reversed.
- zonidjan 7y agoMeh. Every 10F difference is a bit under 5C difference (since the ratio is 9:5). So you can estimate that 40F~5C, 50F=10C, 60F~15C, etc. All I remember is 2:1 and 32F=0C.
- greggyb 7y agoI find it helpful to do similar, but mine is fuzzier and tied to day-to-day activities. I am a gross farenheit user, so this is my mental table for cross reference -42|-42: 9th layer of hell 0|32: freezing point 10-15: maybe think about a jacket 20-25: room temp 37|98: body temp 50: death valley 100|212: boiling It's not precise, except for some intersection points, but it sticks well for me and allows me to be conversational enough to impress metric-folks when I convert my temps to rough Celsius for them. It's rare to need precise temp in conversation.
- sgentle 7y agoI use "double and add 30" (or "minus 30 and halve" for F->C). The accuracy isn't that great, but it's within single digits between freezing and boiling. More than good enough to parse "oh my god it was like 40 degrees outside" as being a meaningful statement about the weather.
- jypepin 7y agoand it has never failed me! +1
- gus_massa 7y agoIf you want to get fancy, you can call it the Taylor approximation. I'm a bit lazy so I try to use the F(c)= 2 * c + 32 approximation described in a sibling comment, but for the range of human-friendly temperatures the error is too big. The problem is not the absolute difference, but how each temperature feels. So I have to resort to making the exact calculation or using Google for the conversion. I'll try your method in the future.
- tzs 7y agoJust go back 10% after computing 2C and the result is exact. If you don't want to deal with non-integers, round to the nearest integer when taking 10%. The final result will be the exact result rounded to the nearest integer. Example: 22℃ -> 44 - 4 + 32 -> 72℉. (Exact is 71.6℉) Example: 23℃ -> 46 - 5 + 32 -> 73℉. (Exact is 73.2℉) I've seen people do the going back 10% before the doubling. That's fine if you are not going to round. If you are going to round, take off the 10% after the doubling or you could end up off by up to 1℉ for the final rounded amount. For example, 26℃ with rounding after -> 52 - 5 + 32 = 79℉ (78.8℉ exact). With rounding before it goes -> (26 - 3) + 32 = 78℉.
- Jedd 7y ago> ... while 68 and 86 are reversed. Just had a flashback - my mum giving me a comparably helpful mnemonic about four decades ago: 16 (c) ~= 61 (f). That, along with human body temperature (38C ~= 98F) have stuck, and between them I can guesstimate most numbers in between on the foreign (F) scale.
- robocat 7y ago37°C (not 38): 37 is a prime, and a centered hexagonal number, if you need some facts to hang your memory on. It's only approximate (same for °F where 98.6 is now seen as "normal"). "Normal" temperature depends on where on the body you measure anyway.