Science, Tech, Math › Science Specific Gravity Definition and Values What Is Specific Gravity? Share Flipboard Email Print Specific gravity is used to determine alcohol content of beer. LYagovy / Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated January 15, 2020 Specific gravity is the ratio of the density of a substance to the density of a reference substance, which is usually water for liquids and air for gases. When water is used, it is at its highest density, which is at 4 °C or 39.2 °F. When air is used, it is most often room temperature air, at 20 °C or 68 °F. Pressure is most often 1 atm. However, conditions of temperature and pressure should be specified when stating a specific density value. Specific gravity is also known as relative density. Specific gravity is a unitless value. Example Values The specific gravity of pure water at 4 °C is 1. Other values are: Ethanol: 0.78Urine: 1.003-1.035Blood: 1.060Table salt: 2.17Iron: 7.87Lead: 11.35Osmium: 22.59 Sources Hough, J.S., Briggs, D.E., Stevens, R.; Young, T.W. (1991). Malting and Brewing Science, Vol. II Hopped Wort and Beer. Chapman and Hall. London.