A beer brewing hydrometer is a device designed to measure the density of a liquid. This density measurement is known as the liquid’s Specific Gravity. Hydrometers are calibrated based upon the specific gravity of water at 60°F being 1.000. Liquids denser than water will have a higher specific gravity and liquids with a reduced density will have a lower specific gravity.
To use a hydrometer for beer brewing, fill a test jar with the wort to be measured. Place the hydrometer in the jar, giving it a spin to dislodge air bubbles. Once the liquid has settled, take the measurement reading from the scale on the side. In order for the measurement to be accurate, the sampled liquid must also be at 60°F. If the liquid is not at 60°F, then the measurement must be adjusted. The beer brewing hydrometer correction calculator above will help you calculate the correct Specific Gravity based upon the temperature of the solution being measure.