Boiling point of water and altitude

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Gone but not forgotten. RIP
Original poster
OTBS Member
SMF Premier Member
Jun 21, 2007
When checking your thermometers for accuracy remember that altitude does effect the boiling point of water. The boiling point for water is 212* at sea level. For every increase of 500 ft. in altitude, the boiling point of water will decrease by 1*. This may not seem as much, but at some higher altitudes there willl be a difference of several degrees. I'm at 187 ft. above sea level, but I can't split degrees on my thermometer so my boiling point of water is 211*. Just don't think that the thermometer is off by so many degrees without considering the altitude. I know this may be overkill, but some techies will enjoy it.
ok..that being do the people in the higher altitudes calibrate their thermometers ??? I,m about 4000 ft. (3733 ft.)
At 4000 ft. above sea level you divide that by 500, and you get 8. For every 500 ft. it drops 1*. So your therm should read 204* (212* minus 8*) at the boiling point of water. If your therm reads differently, mark down the diiference. I hope this helps, let me know the results of your testing. You''ll often find this info. on boxes of cake mixes.
* As a side note, when I first went to Twin Falls the population was 38,000 and elevation was about 3800 ft. above sea level, at that same time Idaho Falls had a population of 48,000 and an elevation of 4800 ft. above sea level. My how cities have grown.
That's what I thought. ( Just wanting to be sure ). Have 1 therm correct, others + /- by 5*. Thanks for the info.
Beware! The calculator at that link can give false values unless you realize and understand a very important thing!

It only asks you to enter Barometric pressure, and will then display the boiling point of water at that pressure. The problem is, if you obtain your local barometric pressure from an online service like or other web site, is that the pressure they list for your area IS ADJUSTED FOR SEA LEVEL! [font=Verdana,Helvetica,Arial]To perform a valid boiling point calculation, the calculation MUST include your elevation so the sea level adjustment can be "undone". [/font]In other words the primogrill calculator will only work if you have your own barometric pressure gauge.

A MUCH better calculator to use is the one at
You enter your elevation and your adjested barometric pressure and it'll display the correct boiling point of water.
Great observation coyoterick!
The method I use is the ice water method. Fill a drinking glass 1/2 - 3/4 full with ice cubes and then fill the glass with water and let it sit for about five minutes. Stir the ice water and insert the thermo. If your thermo is calibrated it will read 32*. If not adjust the nut on the back so that needle will read 32*. This is the method that has been give in every food handlers class I've attended. The reasoning is water boils at different temp depending on altitude but it all ways freezes at 32*.
Good point Dutch, I use the ice water method too. My thermos are digital, do you know if there is any way to adjust those little buggers? All 4 of them are off, some, as much as 14 degrees.
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