A Thermometer used for homebrewing purposes needs to measure to at least to water's boiling point (212°F/100°C), and perhaps as low as freezing. A floating candy thermometer is a good choice for measuring the temperature of wort, especially if mashing. A stick-on thermometer, or fermometer is useful in determining the temperature of the beer in the carboy or fermenter, to know the right time to pitch the yeast, or to make adjustments to hydrometer readings.