PPM Definition (Parts Per Million)

What PPM Means in Science

PPM or parts per million is a unit used to express dilute concentration of chemical solutions.
PPM or parts per million is a unit used to express dilute concentration of chemical solutions. Martin Leigh / Getty Images
by Anne Marie Helmenstine, Ph.D.
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.
Updated July 24, 2017

PPM Definition: PPM stands for parts per million. It is commonly used to express concentration and temperature coefficients.
 

Also Known As: parts per million

Examples: 100 ppm is identical to 0.01%