For the students of science and economics it is absolutely necessary to learn how to calculate errors. So, here is an easy guide to learning different types of errors with a special focus on the various ways to calculate percent error. Errors are introduced in calculations during the measurement of a quantity. These are mainly of three types: Systematic errors Random errors Human errors Systematic Errors Systematic errors arise because of a fault or imperfection of the measuring instrument. For example, if the instrument is handled in an incorrect way it might give incorrect values or there is a fault in the construction of the instrument. Random Errors Random errors are unpredictable changes. These can arise due to change in the measuring device or the environment. For example, electronic noise, irregular heat loss due to wind, etc.