Percent error, sometimes referred to as percentage error, is an expression of the difference between a measured value and the known or accepted value. It is often used in science to report the difference between experimental values and expected values.

Find the percentage. For percentage change, divide the answer by absolute value of the old value; for percentage error, divide the answer by the exact value. For the percentage difference, divide the answer by the average of the two values. Once the final

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.