# Percent Error Calculator

getcalc.com's Error Percentage Calculator is an online basic math functions tool to find the difference between observed (practical) and theoretical (expected) score in percentage with respect to theoretical score. To calculate X% of Y, X is what percentage of Y, percentage difference, change, increase or decrease, use the below calculators

## Definition and Formula: Percent (%) Error

**Error Percentage** is an important mathematical function used to measure the practical and theoretical values difference in percentage with respect to the theoretical value. For example, the expected radius of a machining bolt is 9 inches but the observed is 8.7 inches, then what is the error percent? The answer is 3 percent. Similarly, the percent error is applicable in most of the applications wherever the expected and observed score is comes into effect. It’s mostly used in the field manufacturing, finance, statistics etc.