Science, Tech, Math › Science Absolute Error or Absolute Uncertainty Definition Chemistry Glossary Definition of Absolute Error Share Flipboard Email Print Error reflects the amount of uncertainty in a measurement. Wladimir Bulgar / 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 August 09, 2019 Absolute error or absolute uncertainty is the uncertainty in a measurement, which is expressed using the relevant units. Also, absolute error may be used to express the inaccuracy in a measurement. Absolute error may be called approximation error. Absolute error is the difference between a measurement and a true value: E = |x0 - x| Where E is absolute error, x0 is the measured value and x is the true or actual value Why Is There Error? Error is not a "mistake." It simply reflects the limitations of measurement instruments. For example, if you use a ruler to measure a length, each tic on the ruler has a width. If a distance falls between marks on the ruler, you need to estimate whether the distance is closer to one mark than the other and by how much. This is error. The same measurement may be taken multiple times to gauge the range of the error. Absolute Error Example If a measurement is recorded to be 1.12 and the true value is known to be 1.00 then the absolute error is 1.12 - 1.00 = 0.12. If the mass of an object is measured three times with values recorded to be 1.00 g, 0.95 g, and 1.05 g, then the absolute error could be expressed as +/- 0.05 g.