Measure original gravity (OG)
Specific gravity measures a liquid's density relative to the density of water. A number greater than 1.0 means that the liquid is denser than water, while a number less than 1.0 means the liquid is less dense. Here are a few common specific gravity measurements:
| Substance | Specific gravity | |
| Pure honey | 1.450 | |
| Sea water | 1.025 | |
| Pure water | 1.000 | |
| Pure ethanol | 0.787 |
Specific gravity is important in brewing because it tells you how much sugar is dissolved in the wort or beer. An original gravity reading is taken before fermentation and indicates how much potential is available for alcohol production. Here are some common original gravity readings by style
| Beer style | Typical original gravity | |
| Lite American lager | 1.028–1.040 | |
| Irish stout | 1.036–1.050 | |
| American IPA | 1.056–1.075 | |
| American barleywine | 1.080–1.120 |
On the next page, Steve will demonstrate how to take an original gravity reading.