When testing the accuracy of a thermometer in boiling water, it's important to know the boiling point of water at your location, especially if you live at high altitude. The boiling point of water is influenced mainly by atmospheric pressure, and atmospheric pressure varies based on your altitude and current weather conditions. Since weather conditions change from day to day, it's best to determine the boiling point of water right at the time you are about to test your thermometer.
Here's a calculator that estimates the boiling point of water based on your current barometric pressure in inches of mercury (inHg) and your elevation in feet.
Why Do I Have To Provide My Elevation?
The barometric pressure for your location that is reported on the Web or on television has been adjusted to sea level. To perform a valid boiling point calculation, you must provide your elevation so the sea level adjustment can be "undone".
If you have a barometer at home with a pressure reading that is not adjusted to sea level, just enter zero in the Elevation field.