Science, Tech, Math › Science PPB Definition in Chemistry (Parts Per Billion) What Does PPB Mean in Chemistry? Share Flipboard Email Print PPB or parts per billion is used to describe concentration in extremely dilute solutions. Glow Images, Inc / 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 March 05, 2019 PPB stands for parts per billion. One part per billion is one part of solute per one billion parts solvent. PPB is a commonly used unit of concentration for very small values. The "parts per" notation is not part of the SI system of units. The notation describes dimensionless quantities. The ppb notation is most often seen in physics and engineering. In chemistry, the use of SI-compliant units is encouraged. Source Schwartz and Warneck (1995). "Units for Use in Atmospheric Chemistry." Pure Appl. Chem. 67: 1377–1406.