Percentage error is a way to express how much a measured value differs from a true or accepted value. It is calculated by taking the absolute difference between the measured value and the true value, dividing that by the true value, and then multiplying by 100 to get a percentage. This helps to understand the accuracy of measurements in various fields, such as science and engineering. For example, if a scientist measures a length as 50 cm, but the true length is 52 cm, the percentage error can be calculated. The formula would show that the error is about 3.85%, indicating how close the measurement is to the actual value.