This Percent Error Calculator (% error calculator) will calculate the percentage error between an experimental measured value and a theoretical actual value. Percentage Error Formula\( \text{Percentage Error} = \dfrac{ ET }{ T }\times100 \) Where E is the experimental value and T is the theoretical value. This formula is similar to percentage change. For example, how to calculate the percentage error: Suppose you did an experiment to measure the boiling point of water and your results average to 101.5°C. This is your experimental (measured) value. We know that the actual boiling point of water is 100°C, so this is your theoretical (actual) value. What is the % error between E = 101.5°C and T = 100°C? Plug numbers into our percentage error formula \( \dfrac{ ET }{ T }\times100 \) \( = \dfrac{(101.5  100)}{100} \times 100 \) \( = \dfrac{1.5}{100} \times 100 \) \( = 1.5\% \; \text{error} \)
Percent error or percentage error expresses as a percentage the difference between an approximate or measured value and an exact or known value. It is used in science to report the difference between a measured or experimental value and a true or exact value. Here is how to calculate percent error, with an example calculation.
Percent error is the difference between a measured or experiment value and an accepted or known value, divided by the known value, multiplied by 100%. For many applications, percent error is always expressed as a positive value. The absolute value of the error is divided by an accepted value and given as a percent. accepted value  experimental value \ accepted value x 100% For chemistry and other sciences, it is customary to keep a negative value, should one occur. Whether error is positive or negative is important. For example, you would not expect to have positive percent error comparing actual to theoretical yield in a chemical reaction. If a positive value was calculated, this would give clues as to potential problems with the procedure or unaccounted reactions. When keeping the sign for error, the calculation is the experimental or measured value minus the known or theoretical value, divided by the theoretical value and multiplied by 100%. percent error = [experimental value  theoretical value] / theoretical value x 100%
In a lab, you are given a block of aluminum. You measure the dimensions of the block and its displacement in a container of a known volume of water. You calculate the density of the block of aluminum to be 2.68 g/cm3. You look up the density of a block of aluminum at room temperature and find it to be 2.70 g/cm3. Calculate the percent error of your measurement.
Percent error is related to absolute error and relative error. The difference between an experimental and known value is the absolute error. When you divide that number by the known value you get relative error. Percent error is relative error multiplied by 100%. In all cases, report values using the appropriate number of significant digits.
