ThermCal is a small handy app for use in calibrating thermometers. Instructions are provided in the app as to how to take readings with a thermometer and the app then computes the adjustment if needed to be made on the thermometer. Since altitude impacts the boiling point of water, the app can use your phones location to get your altitude or it can be entered manually. Altitude is factored into the calibration calculation. You can easily switch between Celsius and Fahrenheit. Your first 25 calculations are free and after that you can upgrade once via in app purchase to unlimited calculations for only $0.99.